Alright, here's my setup:

Intel i7 with 2.67GHz
6 GB DDR2 RAM
NVIDIA 260 GTX, which has 896MB onboard RAM.

2 Seagate Barracuda HDDs, one used mostly for system and misc. apps, the other entirely for media and game storage. The first is a 500 GB model still with 253GB of free space, and the game drive is a TB model with 750GB still free, both are defragmented weekly.

I run the game at my native resolution of 1680x1050, almost every graphic option as high as it will go except for AA that I like to keep low(seems to be the usual kicker...). Does it seem like I should still encounter significant stuttering with that setup? Outdoors is of course the worst part, when literally whenever I turn, or look at the sky, I get massive stuttering with no relief, but the stutters seem to have begun to creep into indoor areas too. I just did Mothership Zeta for the first time, and more than a couple times the figths with multiple aliens had massive stutter hiccups everytime I tried to turn. I know I'm pushing it a little, but I've begun to lower the distances on several of those options and it seems to me, even as much as FO3 pushes it, my setup should be handling it at least a little bit better than it is I've disabled all background apps, set FO3.exe to disable the desktop etc. Am I just overestimating my rig, or am I possibly missing something important here? I'd be appreciative of any advice! Thank you.

How many cores is your processor? I have a 2.6GHz Quad and it runs fine, but a 2.6GHz dual might have trouble. I'm not sure about that though, and other than that I don't see anything wrong. (If you haven't already done it, go to the launcher->options->default/auto-detect settings. This will set the settings to fit your system so you don't have to figure it all out yourself.)

With that setup, the auto-detect should put all of your settings at ultra-high or high. Your rig is a lot better than mine, and it runs at ultra-high settings, no problems at all.

Try fallout 3 stutter remover.