I'd been looking forward to this one since I saw that first teaser trailer many months ago, and bought it as soon as I saw it had been released.
In short, it's a really good game! It does tend to get a bit repetitive - each assassination follows the same process: go to city assassin's bureau, get information, go out into the streets and get more information by eavesdropping on conversations, pickpocketting information or interrogation (by beating a target up until he gives you the information), go back to the bureau, then make your way to the target, kill him, fight off a few guards, then run!
There isn't great variety in the gameplay, but what gameplay there is, it works really well. The control method is very simple - four direction movement keys, mouse-look, LMB to attack, RMB to move from low profile to high profile, and one key each for head action (e.g. eagle vision, which marks out hostiles), hand action (e.g. grab, pickpocket) and leg action (leaping from building to building).
Combat is simple in principle, but can be tricky in practise. Rather than wade in hacking with your sword, the better tactic is to wait for the opponent to attack, then you counter. This is as simple as holding down the RMB and moving around, and as soon as you see the opponent attack, you press the LMB. It's not QUITE as easy as it sounds - the timing must be very good! But it needs to be simple, because you often find yourself surrounded by 7 or 8 enemies!
The "free-running" mode works brilliantly too. No timing required here! You simply point Altair in the right direction, go into high profile mode (by holding down the RMB), run forwards, and hold down the leg action button (space by default). The character takes care of looking for things to grab on to, or knowing when to jump. And at this point, I'll have to mention the aesthetics! The character animation is superb!
Might as well carry on with aesthetics now then. The graphics are fantastic! The view distance is quite literally miles - from the top of the towers, you can see the whole of the city, and literally plan your next move, and there is very little (if any) noticable slow-down as a result*. The three large cities are very well built - they feel like a real city, especially with the large number of people walking around.
The sound effects are mostly very good too, although walking past a street preacher saying the same two or three sentences over and over again can be a bit annoying!
Anyway, in short:
Good: Graphics and animation, sound, general game play. Some great satisfaction in planning and pulling off a kill.
Bad: A bit repetitive, at times a little bit frustrating, and those bleedin' beggars who keep getting in your way - you want to punch them, but you don't want to alert the guards...
Bottom line: Great game, well worth buying.
PS - I was a little bit disappointed that I didn't get a free Jade Raymond in my Director's Cut edition... ;o)
* my specs: Intel C2D E6600, GF8800GTS(320), 2Gb RAM, Win XP Pro