Users of the latest released version of Firefox should not expect their add-ons to work properly with this beta.
Please note that installing Firefox 3 Beta 1 will overwrite your existing installation of Firefox. You won't lose any of your bookmarks or browsing history, but some of your extensions and other add-ons might not work until updates for them are made available.
http://www.mozilla.com/en-US/firefox/3.0b1/releasenotes/
You guys might want to, like, read the release notes dudes. :