ProStreet is a game with an identity crisis, and I think a lot of people who buy it are going to be either confused or irritated by this. It's also riddled with annoying bugs, though it is largely playable.
While ProStreet gives the initial impression that it's something to do with street racing, it's not. In fact, ProStreet is all about track racing, albeit production cars. In fact, the name sould probably have been ProTrack, suggesting production track racing. The closest equivalent product, and seemingly the inspiration for much of the content of the actual game is Gran Turismo A-Spec. The 'street' element of this game is almost entirely window dressing. The badly designed, and difficult to use menu system attempts to affect a bit of the US ricer/street-racer culture style, and there is an extremely annoying commentator who attempts to inject a little bit of street colour into proceedings, but make no mistake, this game is substantially different from its aging predecessor "Need For Speed: Underground 2", which was about actual street racing. The 'Pro' part, whether it's supposed to mean professional or production, is suitable enough I suppose, but you can forget the street - many of the tracks are not even substantially urban.