I fall asleep stoned pretty much every day. It's never been the least bit problematic for me, in fact, it just amplifies my going-to-bed routine, which makes it easy to fall asleep.
MyDoors' going to bed routine:
* Shower
* A cup of warm chai, made with decaf tea
* An album of something ambient or cosmic
* A chapter of a book
* 100mg of 5-htp
* A bowl o' dank
The tryptophan in the 5-htp and the warm milky chai get me plenty sleepy. I can usually sleep six hours and wake up feeling like a million bucks after this routine.
Before I ever touched any drugs, prescription or recreational, I used to be one of those people who needed 9 hours of sleep JUST TO GET BY! If allowed to sleep my fill, I'd go 11 hours typically. The sleep would always be shallow and mostly dreamless. It would take me easily half an hour to fall asleep, and if something roused me, I had a very hard time falling back asleep.
Since getting into weed and 5-htp, I've been sleeping like a champ!