A decent platform game, nothing more or less
Gameplay: The setting is the most interesting part of the game. It is set in Renaissance Italy amidst a lot of political intrigue and infighting. Ezio, the protagonist, is trying to uncover a somewhat murky plot while learning the assassin's trade. At the same time, Ezio has a present-day counterpart who shares consciousness with him and can assist in the age-old fight between the Templars and the Assassins. The story is really not the strong suit of the game and is largely forgettable. However, there are a number of quests that are interesting.
The controls are fairly simple and straightforward. Fighting involves timed button input, and movement is controlled largely by the analog sticks. Ezio can get involved in a lot of things in and around Florence, including treasure hunting, pickpocketing, assassination contracts, beating people up, and upgrading a villa. Nonetheless, the routine of it all gets a bit boring after a while and seems to lack real purpose. If you stick with the main storyline, this game should last about 15-20 hours.
The real test of whether you'll like this game is whether you enjoy platform games. That is, how much running, climbing, jumping, and chasing can you tolerate over the course of several hours. For me, the jumping in particular got monotonous early on. For about the two hours of the game, skipping along rooftops is cool. It even looks good. However, after you've chased 3-4 people all over cities and catacombs--and fell to your death a few times, the novelty tends to wear off. Unfortunately, this issue is not mitigated by other aspects of the game. The assassination and stealth dynamics are not particularly engaging and are much better done in games like Hitman and Thief. Anyhow, if you like this sort of platforming, you'll probably like AC2.
Graphics: The game looks quite good. God of War 3 is still the best-looking game that I've seen on PS3, but AC2 does have its share of eye candy. The cities and countryside look especially picturesque. Character models and animations are decent, though they are often repeated.
Sounds: The audio is well done. Most of the voice acting is with Italian accents (or in Italian). Sound effects are convincing, and the orchestral soundtrack adds to the atmosphere.
Replayability/Value: For those who like these kinds of platform games, this is a decent game for the price (now about $20). Don't expect much in the way of replay value, unless you don't mind the collection-oriented side quests (such as looking for 100 feathers and raiding catacombs). I can't strongly recommend the game except for those who enjoy the climbing and jumping aspects, which are in abundance. For others, there are better games out there.