My pc is a year old and the game is almost glass smooth with all the default visual settings at 1024*768. A realief aftre the huge lagginess of Oblviion.
No AA on though. I haven't even tried increasing any of the settings since I think it looks fine, although the jaggies are there when you lean. There is a very occasional hitch here and there when something appears to be loading, but its incredibly brief.
my pc basic stats: 2gigs ram, Pentium 4 3.6, 3950 GTX
You've got 4 times more ram than i do, and your graphics card is better (i think, i've got a radeon 9800 pro)
I really really hope the game will run on med to low settings, after all HL2 and Farcry both run silky smooht on medium.