You gotta play it at least once, you wont regret!!
First i will start with the gameplay which it is very good, I will give it a 9.5
Graphics: 8 out of 10, you know, have you ever played GHII? It has "good" graphics, but in GH III the improved, but not that much we wanted to see.
Content: 9 out of 10, good playlist, store things are good and more variety than other GHs, cool characters and i think it will have a lot of good downloadable content from Xbox Live, the only thing im not feeling that much is the playlist, you know cool soundtrack, but something is missing.
Another thing I liked, is the fact that it has online play. The things i didn't liked, were the HARD achievements and the difficulty of the songs the final songs in hard are like in expert.
The final fact, if you are a fan of GH games, you must buy it.