I'll put down a few thoughts I have about this poem -- please correct me if I seem ridiculous. :)

I see the first three lines as a wonderfully evocative description of thunder and lightning. "To pile" makes me think of both the huge storm clouds themselves and the way that thunder (in its most cliche verb) rumbles, often to a kind of climax (the "close"?), before it crumbles "grand" away. This is in contrast to the third line, which I think is about lightning -- evoked in the way it illuminates everything "created" for an instant before creation is "hid" in darkness. Thunder, which is of a much longer duration than lightning, gets fittingly two lines, with lots of deep and open vowels like "u", "o", "a." Lightning, on the other hand, really only occurs in the last two syllables of the third line: "...everything created" illuminates the world in our minds, and it's instantly cast back into darkness with the subsequent "hid." This has a nice bit of internal rhyme there (-ted hid), and the sound of the short "i" is of a higher pitch than the previous vowels. So, thus far, we so far experience the thunder rumbling grandly, followed by a flash of lightning.

Interestingly, Dickinson chooses to describe lightning after thunder, even though thunder occurs after lightning does. Of course, in a thunderstorm with lots of lightning, you rarely get orderly sight-sound occurrences -- very often, lightning hits again at the end of a roll of thunder. This tells us that the thunderstorm is a big one and not an isolated cumulonimbus. More than that, it's appropriate, given how Dickinson uses this as a metaphor for poetry and love.

Formally, the poem can be broken into two quatrains. The first ends on "Poetry" and the second begins with "Or Love." There is a symmetry with regards to the capitalized elements -- "Thunder" on the first line, then "Poetry," "Love," and "God" on the last line. This chiasmus is not only an aesthetically interesting and satisfying arrangement, it encourages comparisons and cross comparisons within each paired set of elements. The rhyme scheme also ties the poem together. "away" has an eye rhyme (or slant rhyme) with "Poetry" in lines 2 and 4 for the first quatrain, and "prove" and "live" rhyme in lines 2 and 4 for the second quatrain. Lines 1 and 3 of Q1 ("close" and "hid") do not rhyme, whereas in Q2 "came" and "consume" rhyme (and imo, one of the most wonderful rhymes I've seen in months!). This asymmetry of rhyme is fitting, because the first three lines (underscored by the aforementioned "created" "hid" rhyme) are a semi-independent entity of description/exposition. The last three are a semi-independent entity of philosophy/abstraction, but it is linked by the Q2 L1,3 and L2,4 rhyme to the body of the poem -- and more tightly to what came before. Thus there's both symmetry and asymmetry at work, which is fitting given Dickinson's subject and aesthetics. Love is like poetry, thunder is like God, but love is not poetry and thunder is not God; we can grasp and experience both love and poetry, but, at the same time, we can't, because they are abstract, ephemeral concepts greater than we are.

The second half of the poem, to me, is both an enactment and exposition of the idea of the linkages between poetry and love, as well as our inability to grasp them. "Or Love" comes quickly after "Poetry" -- as quickly as lightning after thunder. (Indeed, it is even more appropriate, imo, that the lightning should follow thunder in this poem, because it underscores the unexpectedness of the event -- we always expect the thunder after lightning, not the other way around.) Typical of Dickinson, these huge, abstract concepts are juxtaposed to a much smaller scale. "-- the two coeval came --" states that the two concepts are contemporaries, but it also suggests, by virtue of the two concepts being lassoed into "two," that we can grasp them. This is like referring to God as "he" instead of "He," or the Holy Trinity as a mere "they" or "the three." The next two lines are difficult, and, I think, intentionally so. "We both and neither prove, / Experience either, and consume --" The "we" is the subject of "prove," "experience," and "consume," but the ordering of verbs and punctuation makes this sentence quite torturous. It's as though the speaker were grasping for something that eludes her, and which builds on and on with each comma. I want to make particular note of the verb "prove," which I think is crucial to the poem. "We" -- humans -- are the ones who will prove poetry and love (these two concepts, which are related to God!). It's a blasphemous -- and utterly modern idea. Without humans, how would there be love and poetry and God? At the same time, these things are greater than we, so we can't prove them, we can't justify their existence. (It seems to me that this totalizing line also echoes the thunder-lightning rhythm, with "both and neither" as a buildup to the lightning-like verb "prove".) In the next line, the speaker tries to modify the categorical "both and neither" into a lesser "Experience either," which puts us on a lower plane of authority in relation to the two abstract concepts, and gives a choice between the two. However, this compromise quickly leads to "consume --", which is quite a terrifying verb. It seems initially impossible -- can we consume "Love" and "Poetry?" If we can, doesn't that make us monsters, treating both as the meat for our sustenance, like the cyclops eating men? Or does it mean, as it is suggested by the three times the object is mentioned ("both" "neither" "either") after the subject, that "Love" and "Poetry" will consume us? Finally, in a different totalizing gesture, the poem ends with "For none see God and live." This line is notable for its austerity -- all the words are monosyllabic, and only "see" has a Latin root. The judgment of poetry and love and our relation to it seems reserved for God, and whose judgment will be so totalizing that it's impossible to live after that. (I want to add, though, that I don't see this God as being the same sort of God as Herbert's -- this God is on equal footing as Thunder, Love, and Poetry, imo it's like a view towards divinity.)

Thanks, Angstrom, I think you've gotten the reading off to a very nice start.

To begin my own reading, I'd like to ask: What do we make of all these sight rhymes?

(The relationship of 'came' to 'consume' is one place where I would have to differ with Angstrom; I can't imagine these as more than a sight rhyme, and not even really quite that, just like prove/live.  I would also say that there is barely even a sight rhyme in the first quatrain.  On the other hand, we should notice the internal slant rhyme of Love/prove and the internal rhyme between 'neither' and 'either,' which I'll try to remember to discuss below.  There are some other structures linking disparate parts of the poem, like the parallel, delayed alliteration of pile/Poetry and Love/live.)

In answer, I would suggest paying attention to the ways that visual and auditory registers are invoked in the poem.  Angstrom has already pointed out how lightning is implied but never mentioned in lines 1-3, which name the state of non-visibility after the lightning flash (when "everything created hid").  I would suggest that this incompatibility or out-of-joint-ness is the poem's conceptual pivot.  Here it's imaged as the delay between thunder and lightning, and the poem names the one while eliding the other.  Each marks an upper limit of perception by one sense.

The last line's reference to Moses offers one conceptualization of these upper limits: 'God' appears to name what transcends the possibility of representation.  Let's call this the Judaic model of transcendence.  I want to mention a second model that's not explicitly named here, but that I think turns out to be important: the Greek model, according to which you cannot hear the truth and yet retain your sight.  (Compare the story of Oedipus, who puts out his eyes after hearing the truth, with the cultural tradition concerning the blind poet Homer.  Knowing and hearing/speaking are mainly equivalent in this tradition.  Another difference between the two models is that the Greek model may not involve intensity or magnitude: Oedipus isn't blinded by light.)

Dickinson's poem seems to me to operate in several gaps and differences:

(1) The gap between perception and sensation.  By perception I mean the intentional orientation toward an object, instead of mere sensation (e.g. an apple instead of the sensation of red light, or more problematically a word or musical piece instead of a stream of sound).  I would say that thunder and lightning, in addition to marking an upper limit of perception, are barely objects at all -- they are closer to raw sound and light.  As figures of perceptual limits, they seem to suggest that above these limits it would be impossible to organize our senses and perceive objects at all, that we would instead be subject to overpowering sensation.

(2) The gap between visual and auditory senses.  Angstrom has already pointed out the thunder/lightning image of this gap in lines 1-3; and I've said that I take this gap to be the meaning of Dickinson's use of visual rhymes here.  In lines 6-7 the model of mutual exclusion is repeated with regard to Poetry and Love: "We both and neither prove - / Experience either and consume -"  (As clarification, I think it would be useful for me to claim that the primary sense of 'prove' in these lines is not 'demonstrate' but 'try' or 'test,' which are almost synonymous with 'experience'; and that 'consume' isn't transitive: "we" aren't consuming poetry or love, but instead we consume – waste away, or are burned to ashes – if we experience either of them.)  The speaker is not only claiming that we are destroyed by experiencing either, but also that we cannot therefore experience both.

(3) The difference between one transcendent term and two.  The incompatibility of supreme sound and supreme sight recalls the Greek tradition in which one cannot perceive the truth in both ways; but the last line invokes the Judaic tradition in which there is a single kind of transcendence (visual), which is so overpowering that it kills the mortal man, whereas nobody (as far as I can recall at the moment) ever died from hearing the word of God.  Similarly, the poem posits two transcendent terms, 'Poetry' and 'Love,' and it cannot decide if they are one or two.  They "coeval came," but lines 6-7 pose an irresolvable conundrum.  If "We both and neither prove -" then in spite of the union of contraries ('both' and 'neither': does this suggest a partial experience of both, or the opposition between a complete experience and none at all?), at least the two are aligned; but then line 7 says that either one of these, alone, destroys us.  The only true rhyme in the poem, 'neither'/'either,' elides this problem, and I would say it's deliberate that the words are not so much rhymed as identical (at the level of the spoken or written word), while the added N produces complete inversion (at the level of the signified meaning).

Beside the structuring mechanisms that I've mentioned, these three oppositions are organized by the global structures of symmetry and asymmetry that Angstrom has already pointed out.

What would be the activity of the poet, then?  I don't think that this poem is substantial enough to afford a clear sense of Dickinson's answer, but it sketches a direction ("This - would be Poetry - ": notice the hypothetical mode, which matches the line's interruption of rhythm and refrains from even naming poetry unequivocally).  If poetry is concerned with what transcends the limits of possible experience, which seems to be the case here, then it might be reasonable to suppose that the problem is to make it possible to expose or represent this transcendence (whether it's truth, love, God, or poetry itself) without producing destruction, and that the poet must also risk this destruction.  As a first approximation, maybe we could say that the poem's indecidabilities signal the effort.  To speak rather generally: at times this might appear as a balancing act, but at other times it's a question of bringing together contraries into some problematic unity, which might allow glimpses of something beyond them.

I would follow Angstrom in calling the last line a totalizing gesture, and it's a very nice observation that it relies on Anglo-Saxon monosyllables.  (Even 'see' is Germanic rather than Latinate.)  This contributes to the satisfaction offered by its regular rhythm in contrast to that of line 4.  In closing, I just want to add that this final line (which I think has less to do with God's judgment and more to do with his transcendence of our limited capacities) isn't necessarily posited by Dickinson as an adequate closure.  Like my term 'transcendence,' it offers a model of the problem, but it also closes down all the difficulties raised above: it shifts us finally into the realm of vision, offers a stable term (God, instead of the hypothetical Poetry or Love), and in good Platonic fashion substitutes this unity for the earlier pair.  This suggests another problem, the problem of poetic closure, which is something that occupies Dickinson quite a lot, and I think one could bear it in mind as a concern that motivates her a-syntactic procedure in some of the more verbally difficult poems.

***

As a textual note, it might be worth knowing that modern editions, which restore Dickinson's punctuation as much as possible without resorting to a facsimile of her manuscript, add some of her "dashes" (or whatever you want to call them) that could yield a different way of reading some lines, especially lines 4 and 8.  (Since it might be taken as a mistake, I should say that these editions also restore her punctuation of 'it's,' forbidden in modern spelling but legitimate historically.)  Here's the restored punctuation:

To pile like Thunder to it's close
Then crumble grand away
While everything created hid
This - would be Poetry -

Or Love - the two coeval come -
We both and neither prove -
Experience either and consume -
For none see God and live -