Not as good as AC:2 but highly enjoyable with loads of content!!
The story carries forward directly from AC:2 and while Ezio doen't change much, the new characters and the story has a much more continous feel to it. The complaint i had with AC:2 was that it constantly introduced new characters and there wasn't much background to them. The familiar caste and the two new borgias, works better in my opinion. Also both of them are pretty fleshed out with good voice acting and character models.
The graphics are pretty much the same although NPC models react better. Rome looks good but it doesn't have the charm of florence or venice.
Gameplay is great although combat is still too easy. There is a lot more variety to the missions. There is tons of content here. you can loot romulus treasure, destroy borgia towers, kill templar agents, destroy leornado's machines, collect flags, purchase monuments, recruit assassin's. Although i was able to do all of this(except the flags) within 10 hrs along with the main story! Its also easier as you can use your assassin's to do the dirty work for you. All of this along with the unlocked missions mean tons of replayability.
AC:B reaffirms the greatness of this series and is totally worth the endless hours put in it.