Didn't see this link posted here yet, apologies if it was already!
Borderlands PC Tweaks - Gearbox Software Community
I've been PS3'ing in Borderlands with an RL buddy, but had it pre-ordered on Steam (oops). Switching from the PS3 (TV ~10 feet away, thumbstick turning, etc.) to the PC (monitor 3 feet away, mouse turning) actually made me nauseous. The old brain just wasn't falling for the motion simulation on the PC, and it felt... very wonky compared to other PC FPS's, even other Unreal-based games.
Turns out: a couple of edits to the INI helped immensely! Specifically: turning off mouse-smoothing, and pulling back the FOV settings made a world of difference.
The location(s) of the INI's vary, naturally, from XP to Vista to Win7, and also from box install to Steam. Took a few tries to find the right ones, but once I did... totally worth it.
Anyhoot: after I play through on the PS3, I'll probably ramp up a toon on the PC side and join the TOG fun here.
Hope this helps!