Graphical impressions:
AA is in from what I can tell, looks as good as Uncharted 2's implementation, possibly better with polish.
Biggest issue I've noticed is texture pop-in/loading. U3 is pulling some UE3 shit. It's in the customization menus, in the co-op arena, and so forth.
Draw distances don't seem as impressive, but again, this is MP.
Textures and lighting look good and some areas, less than pleasing in others. Hopefully again, is another beta issue.
Sounds:
Everything has much more KICK to it. UMPF!
Gameplay:
Blind fire is crazy fast now, hard to control.
Guns feel great, turning in feels great, hit markers are brilliant.
Huge selection of weapons already, multiple shotguns, micros, pistols, and assault rifles.