Xannies are a relatively new thing for me, something changed about 4 months ago. I used to sleep like a baby then all of a sudden sleep got really difficult.
Weed works really well for getting to sleep, but as you may or may not know, its effects only last an hour or so, 2 tops (more if you ingest it). My issue with sleep is I will wake up in the middle of the night and not be able to fall back asleep. I generally don't go for another smoke in the middle of the night.
Popping a Xannie at 10pm means solid sleep until 10am the next morning if I wanted!