Maryland Dude's theory of smoking weed before bed: sober up a little before sleep (an hour or so for me) and you'll wake up fine. Go to bed stoned and you don't sleep well and wake up out of it.

In fact, my main reason for smoking is because of my insomnia -- if I toke a bit around 9ish I can go to sleep by 11 every time. Without tokage, I'm never asleep before 1am.