Although FF seems very slightly faster, it is a mess. Unlike in the initial testing I did, every single add-on except one was broken by FF3. Not only that, but most of the online things I do get broken by FF3.
I happen to like Windows Live online tools, not one will work right with FF3. I happen to like the integrated login features of my MSN and Windows Live accounts, I like the Live Toolbar and Live Writer, I even use Live Spaces all of which are broken (at least partially) by FF3. It even broke Quicktime, demanding an update (after it worked the first time), which then installed more AppleCrapple I did not want.
I'm not a fan of Google (almost anti-fan), yet the search bar is installed as requisite to the browser and there is apparently no way to get rid of that.
Uninstall left junk behind, thanks goodness a System Restore took care of most of that. I still ahd to do a registry sweep, and I hate doing those because lord know what THAT will break.
All in all, as a "common man" end user (well, maybe slightly more than that, I'm the guy everyone goes to in my circle), I am quite disappointed. As that guy everyone goes to, I am actually not advising people to try FF3. If they bring it up, I will have to warn them that lots of things they like won't work right.