Just a brief post on transferring Firefox 4 passwords from one installation to another.
There are several online resources to sync bookmarks and passwords and while you may be "OK" using these services for bookmarks, you may not wish to use these services for passwords.
Of course you could simply copy all the files in your profile, but which files store your password information ?
Your profile is in ~/.mozila/firefox/profile_name
Your passwords are in two files, key3.db and signons.sqlite
Simply copy these two files to transfer your passwords. Of course, you may wish to encrypt these files ;)
Bookmarks can be exported/imported from the bookmark toolbar (as a html file).