I figure I'll post my issue here. The game keeps getting choppy, even though the framerate is high (stays at 60fps from using d3doverrider). I just recently got a GTX460. I had no issues at all with the new video card. TF2 seemed to perform the exact same.
I just got a new monitor, so I'm running TF2 at 1920x1080 instead of 1280x960. Besides that, no other video settings have changed. The game was working fine earlier today.
It seems to get choppy when at certain parts of maps, sometimes even only looking in a specific direction (usually where there's lots of people and action). Like I said, I have a solid 60fps, and nothing else besides the resolution has changed.