I have the same issue.  I get tons of work done after my BF goes to sleep (he works 7-4 and so he tries to go to bed by 11; my schedule is considerably more flexible).  One compromise that we've come up with involves me laying down with him until he drifts off (about 15-30 min) and then getting back up and doing my work.  The compromise doesn't actually satisfy either of us totally, but it's the best we've come up with so far.  A better idea would be welcome :)

We've also been trying the solution Brian mentions but it's harder than it sounds --- it always makes me sleepy, which makes getting back into work quite slow.

Despite not being tremendously romantic (and often being the one to get up) I've been trying to think about what it is psychologically that makes going to sleep together seem like such an elemental pleasure. Maybe it has to do with the relation to time. Drifting off to sleep one has a certain large distance before things begin again, a feeling of being held indefinitely. I remember being younger and feeling that the night contained an almost infinite reservoir of extra hours, and even into adulthood something of this feeling persists. 

I'm not sure how to reorganize life so as to have these qualitatively different kinds of time in other pieces of the day.

Margaret's post also reminds me of the question sometimes called "work and life."  Is it better to separate the two?  Or to live, according to the popular conception, like an artist?

I would guess that Margaret isn't talking about such a big, alienating division between two parts of life, but about something more like a strategy for dealing with pressures and demands; and it's interesting that childhood could be involved.  I don't know how to produce this kind of effect, except that for me it usually happens by accident.  You can't plan on eating Proust's madeleine, I think.  There might be other approaches, but I thing I would be a little skeptical of them.

On the question of sleeping with a partner, I wanted to add that there could be a practical side to this, apart from the question of what is romantic.  I don't fall asleep quickly, and after getting used to sleeping with my girlfriend, I sometimes have trouble going to sleep at all when she's away.  I'm sure there are things I could try in order to sleep more easily, but I thought it might be worth mentioning here the role of habit and what one is accustomed to.