Installed Firefox 4.0 beta 1 in Mac OS X for about… 5 minutes. For now, loved the reduced size of the toolbar (heh.. where are my bookmarks?.. ok, activated it again). Then, by default text areas are now resizable by the user. Good, as some are quite small (just expanded one at the moment), bad as it can break the page layout. And finally, some problems with my favorite chess website when moving pieces.