Totalidea, the folks that brought you TweakVI, and Tweak-XP Pro have a Firefox "tweaker" now that optimizes your Firefox settings. It's called FireTune and is pretty nice.
I have one minor complaint. The "check box" below labeled "Create backup of configuration" isn't actually a check box. It's a button to create your backup. You'll want to push that button before you do anything. Other than that, no complaints.
