Two other things which are of less importance, but still worth being mentioned here are:
1. The new information bar which appears when prompting the user to change their password. 2. The fact that the Saved Passwords dialog filtering works for the passwords themselves (try hitting Show Passwords on that dialog, and then entering a search phrase; it will be matched against passwords as well as the site and username fields.)
Thanks for the great write-ups on the new Firefox 3 features, BTW. :-)