I can only smoke old skool pollen hash (no paranoia) and I have a smoke right before bed. At first, I let my mind just drift from one mental scenario to annother, sometimes with closed eye visuals, which are normally quite plesant, then I just get heavy, roll over and fall asleep. I believe it helps me drift off well, I feel comfortable and cosy, but I do experience brief periods of waking during the night.
I can definitely say that mj helps me fall asleep, which is always my biggest hurdle when going to bed. But I'm unsure as to how it affects the sleep rhythm and overall quality.