I've been playing for about two or three hours now, and I just made it to Damascus. I agree with Hamstah--the first scene of the city is incredible. The controls are a bit tough to get used to, but the game gives you plenty of tutorial type stuff to get used to it.
The only thing I absolutely hate is how slow Altair has to move. I'm so used to being able to run around in games like this, having to walk slowly to make sure not to offend anyone is really irritating.
Other than that, I'm digging it. I have a massive headache from my shitty TV, though. I think I might play with the brightness a little more to make it better.