I haven't been impressed with Bush at all. If not for his 44 yd. run he would be averaging about 2 ypc. Not what I would expect from the next coming of christ even if it is preseason.
I think Bush could be an absolute killer in an offense like Indys. Just put up some fairly god-awfuls stats.
With the rebuilding 'Aints, however, he's going to have alot of trouble finding any gaps to run through.
That said, and maybe I'll shoot myself for saying something so dumb 10 years from now -- I think Maroney is probably a better fit for the Pats. The 15 or so pounds he has over Bush will definitely help him take more of a beating over the long course of the NFL season, and I imagine he fits in better with the style BB wants to play.
Bush is more of a Marshall Faulk type, while Maroney is more of a Reggie Williams in his prime type (with dreads but without stupid side issues). Both are great players, but in different ways.