BB7's aren't a very big step up in terms of a price, but are a pretty nice step up in terms of design and overall quality.
My bike came with BB5's. Avoid them. Constant adjustment will be required basically after every ride. The rotors that come with them are cheap too - come out of true a lot which can get really old. Spend the extra $$, believe me. I've since replaced with with Shimano SLX hydro's, which, needless to say, is a significant upgrade. But I found a good deal and wanted hydros.