Serious fun, excellent graphics, but tons of memory leaks. After playing for a few hours the game can slow to a crawl and I'm on a GTX 465 1GB card. If you replay a mission b/c you died the game will slow down fast - and finally throw an exception and crash.
I never had such problems, and I completed the game twice, obviously dieing a fair number of times while doing it. ;) I really liked the story, and the ending (SPOILER[?] with obligatory grand shootout :P)
I don't mind it being different than Mafia, the original, it was still very nice. ;)
edit: Also, I was playing on 8800GTS 320/320, C2D E4300 and 3GB RAM, on Windows XP - so not that powerful hardware. It was smooth ride most of the time, with maxed out graphics, 1280x1024 resolution and PhysX turned off (although medium wasn't that big performance hit, it wasn't as smooth anymore, and the benefits of PhysX weren't really worth it that much).
Looking forward to picking this up on Xbox 360. Just have a few games to get out of the way first. I loved the first one. How does this one compare?