I have to say I have played every AC game and each time the atmosphere and graphics blow me away, this is no different. Theres plenty to do outside the main story line with missions for your dens, missions for thieves, romanians etc plus the mini-game of sending assasins to missions. The music and graphics make you slip into the world easily and emerse yourself in the game!
I havent tried the online play as yet as previously I didnt understand the game and kept getting assasinated, but il give it a go in due time.
Apart from this its a defo buy!