Starts off slow but the action keeps building up until you realize this is one visceral experience.
At first I thought the game got off to a slow start and was pretty linear. It was not quiet as open-world as I had thought and throughout most of the game you're doing the same kind of missions over and over again. Basically you go into a city, scale various vantage points to find clues to your assassination target (the boss). Although the mission structure lacks some variety it is very fun carrying out the missions.
I would have preferred if there was more suspense involved in being stealthy and making that a more necessary part of the gameplay but most of the time you'll find yourself alerting too much attention, then fighting off hoardes of guards or jumping roof-top to roof-top as you frantically try to run away and find a hiding place.
I really liked the way sword-fighting was done. It's not just your standard hack and slash gameplay. You have to time certain moves like countering at just the right moment to initiate a brutal counter-attack-kill animation which is so brutal looking and never gets old. It's also about getting into a rhythm of blocking, attacking, countering,parrying depending on the situation and after a while it comes quiet naturally and makes you feel like you're an elite assassin.
The controls are far from perfect though. Often when trying to escape quickly, you'll find your character jumping in a different direction or grabbing onto some ledge you didn't intend. Sometimes these glitches will cost you your life. In any case they get very annoying when you're trying to do something but Altair wants to do something else.
The graphics for me were a let-down. This is the first game I bought for my PS3 and it kind of feels like a quick and dirty port. There are a lot of jaggies, the color is bland and there is major frame-rate issues in large battles. My opinion is probably more harsh because the game's been out a while so it graphics are getting dated. I'm not sure if it was a stunning looking game at it's release or not.
I thought the game got a bit boring during the middle part but in the last 1/4 the action really started getting intense and I found myself getting more drawn into the game and the story. Speaking of story, it's a bit hard to describe because it doesn't seem very coherent. There are a lot of cutscenes where Altair is always talking about doing everything in the name of peace and every bad guy is always trying to justify his evil deeds. The only thing that makes the story any good is that the writer's took the cheap way out by leaving huge holes to be explained in the sequel so you still don't have a clue what's going on unless you buy the second game I suppose.
If you were thinking of buying the game now I would say don't bother unless you get a good deal. Just read the game's story online so you get up to speed then go buy Assassin's Creed 2 which seems to be a much better game in every aspect. Not that this one is bad. I did enjoy this game enough to complete it and the gameplay sets it apart from the rest just enough.