Firefox is made much more Foxy with these tweaks.
No, it’s not just you. Firefox sucks nuts on the Mac. These seem to help.
This second requires you to add a file that doesn’t exist in a stock configuration. It’s called user.js which on my system lives in the same place as MochiKit. So find that directory and create file called user.js that contains one line (for now):
user_pref("nglayout.initialpaint.delay", 0);
You may find stuff to add later, but at least you have the file now.