I'll also throw my opinion into the fray... basically, I think Bully is one of the best games of the last five years. Rockstar really worked to create a compelling story and world, and the result is just spectacular. Unlike most of these open-world games, where the missions soon become tediously repetitive and I end up just driving around and harassing people, Bully has so much variety and creativity in its missions that you really will keep playing just to see what insanity comes next.
On top of that, because the game world is small, the graphics are fantastic and you never feel like you're lost (like in some of the GTAs after GTA3). If you played this on PS2 and you think it's just a straight port, you owe it to yourself to see the carnival section of the game at night time, because it really shows off just what the game is capable of.
One note, however: DO NOT UPDATE THE GAME! There is a single update/patch for the game, but it has been known to do more bad than good. I've had the game for over a year now, and I can clearly state that you do not need to update it... there are no bugs of note in the original release.