I didn't want to de-rail the Consolidated Info thread, but I did want to comment on the INI tweaks kraniac posted.
I still plan to try it out, though, if only during online multiplayer games. I'll likely stick to the stock INI while playing Campaign mode.
The Defiance UT3 FPS INI looks as though it definitely increases performance, but I'm fond of the slightly foggy look that covers the jaggies.I realized after having to look for this information for more than a few minutes that it should go here...
UT3 INI Tweaks thread on MyUnreal: This is a collection of INI tweaks to fix common annoyances and improve graphics performance over at MyUnreal, where the LOB forums are. It's collected from snippets of an extremely long thread over at the official UT3 forums.
Defiance UT3 FPS INI: This is a site where you can download a verified, safe INI that includes the most common graphical tweaks to improve framerates. I use it myself, it's pretty great.
I still plan to try it out, though, if only during online multiplayer games. I'll likely stick to the stock INI while playing Campaign mode.