Lets get the good out of the way first: The game has fairly well designed and unique levels, some unique features, and one of the more interesting stories in the Sonic Universe.
The Bad: Almost every new "feature" that this game introduces is not only un-fun, but actually detrimental to the gameplay as a result of a lazy effort by Sega. The most touted-feature, gunplay, is horribly boring and unbalanced. Only a few weapons have anything that distinguishes them from other weapons, aiming is clunky at best, and they are horribly overpowered: there is almost no reason to use the "jump" attack that is the signature of Sonic games. The backstory is fairly good, and explains the origins of Shadow. However, it is told in a laughably poor way. Due to the "Branching level" system, and the largely meaningless good/evil paths, the only cutscenes that will make any sense are the ones in the beginning and the hidden "true ending". The game also suffers from clunky controls: They are far too "mushy" to allow for adequate control over a character who is capable of moving as fast as Shadow. It is way too easy to misadjust and fall, and sometimes the "jump" attack wiill cause Shadow to blast sideways off a platform, resulting in death. Fortunately, the camera issue is mostly resolved, and the few problems it has could have been fixed with the ability to snap into a "top down" view (which would not have taken SEGA long to implement).
With a little more effort to balance weapons, make the good/evil choice and branching level paths meaningful, flesh out the story, and refine the controls, this could have been an excellent platformer. As such, SEGA's laziness results in a game that plays like an early beta: It plays, feels, and looks like a shoddy, cut-rate production.
The game is alright, maybe not the greatest in the sonic game archive, but acceptable, the guns add a new twist, and the diverse storyline makes it unique, however, some of the missions are really tedious to complete, and when you put it in a 360, the FMV's looks slower and may freeze on you, so i wouldn't recommend putting it in one. overall, its a decent game with some problems but, hey what games don't nowadays huh?