I use 5.1 because my room isn't big enough for 7.1 and since I'm still watching plain ole DVD's, almost everything I come across is in Dolby Digital 5.1. I would not even consider an over head ceiling rear surround option.
The surrounds being for effects only makes them kind of forgiving in the placement department. Besides, you can only put them where you can put them, right?
I don't know much about Bi-poles, so I can't speak on that.