Mp beta has no physics objects though. Im gonna assuming tossing a grenade and watching enemies go flying and tree limbs collapsing is gonna hit the framerate. Also the mp beta is pretty light on foliage compared to some of the vids that have been shown. dx10 as well will obviously hit the framerate.
all talk is suggesting that the game will utilise multiple Cores. i've a Q6600 @3GHz. i'm sure a few physics calculations won't slow the game down on my PC, or most of the gamers on this forum, for that matter.

is there a special edition of it?
not that i've heard of.