If you haven't tried Firefox 3 yet, you should. It's fast.
ftp.mozilla.org
ftp.mozilla.org
I find Firefox 2 to be almost unusable because rendering lots of complex Javascript and Flash eats up an enormous amount of memory. Firefox 3's rendering engine is much better; I'd recommend everyone try it and see if it works for them. There are some other nice new features, like URL auto completion suggesting your most commonly visited sites/directories first.
Use this tool to force your extensions to work with Firefox 3. http://www.oxymoronical.com/web/firefox/nightly
Of course, some of them may cause crashes, but Firebug seems to work without a problem. I'm not running web dev, should I be running it?
Yes, WebDev extension is awesome! http://chrispederick.com/work/web-developer/
The bug I notice the most is text entry/dropdown boxes sometimes not working correctly, this happens most often in a really poorly programmed game I play, http://www.hyperiums.com.
Cons: The bookmark piece needs some polishing, especially in the 'Organize Bookmarks' window.
I've resisted upgrading for so long, since 10.4 never had any particular appeal to me, but it's getting harder and harder to find apps built for 10.3.