I'm on geodon now and was on it about two years ago before stopping, as a regular smoker of cannabis, I can tell you that I have not experienced anything unusual.

When i'm manic/hypomanic it brings me down a bit physically, while keeping my mind slightly more organized so that I can form coherent sentences, while stringing along my thought train. An improvement over just trying to "catch" topics flying through my mind.

On the other hand, if I'm in a depressed phase, it tends to make me forgetful and slightly lazy(er).

As far as helping sleep, maybe for relaxation, zen mode and all. Never done that intentionally, but I usually don't go to sleep without smoking.. so I couldn't give you concrete yes/no on that XD