Lag monster! I don't usually do this, and I love the series up to this game but this has been really frustrating to play. I've been getting lag of over 60 seconds between key press / release and the action happening on screen.
The lag starts out being not too bad then gets noticeably worse on screens with the "XXX Amount of worldwide achievements" appearing. The lag also gets worse the longer the game is played on every screen. After playing for around 10 minutes the lag between input and action gets to around 60 seconds.
I've got nothing else running, a decent video card and about 35% CPU and plenty of RAM free while the game is running.
It's happening the same way on the 2 machines I have:
OSX 10.6 Core2 Duo 2.8GHZ 8GB RAM, Safari
Windows7 Core2 Quad 2.8GHZ 2GB RAM, Firefox
Both with discreet video.
Sorry for the bad rating, but I have to rate on the overall experience I have. I think this is a great game but as it is, on the machines I have, very frustrating to play :(