Yeah, I have the same problem. System's fine (ran Fallout 3 on Ultra last night), but bad lag. Loading times are fine, and it does decent indoors. In combat outdoors with more than one NPC, it's almost unplayable.

I also ran Fallout 3 basically on ultra (Save for no AA). It recommended that I play on High...so I did but turned off AA and once in the game even changed the view distance to lower. But it is very laggy when in combat. The little tutorial with the geckos was not really laggy...but the fight with the gang was basically unplayable.

I even turned the graphics down from HDR to Bloom (which looks like crap) and reduced a bunch of other stuff but it is still glitchy laggy. Half the time you cant aim down the sights and the trigger sometimes does not work...forcing me to go into VATS.

This is exactly my experience. Very frustrating.

Speaking of which, nice to see there is no VATS lag like F3 had.

My game is running a bit better with high settings, 0 AA, 0 AF, and no V-Sync. Pretty sure I can turn AF back up without too much of a hit but I had to eat before I decided to check. Out in the wastelands it's 60+ but like others, as soon a s people show up on screen it nose dives.