The latest
pre-release version of Firefox 3 is available. As a main focus of this release, performance and memory usage are improved. In particular Zimbra, the most heavyweight web application I use, has much better performance when used with this version. A more native look and feel on OS X and Growl notification support are nice features too. It is enough of an improvement that I do not intend to go back to version 2 after experiencing this pre-release.
Most of the extensions I use are working with it now.
Firebug (1.1beta version),
Colorzilla, and
Noscript are all functional. It makes some others obsolete, including some add-ons to incorporate session save options and others to change the way downloads are handled in the user interface.
One particular plugin,
HTML Validator isn't working as I write this. There are
HTML validation bookmarklets available which should help with this issue while waiting, although they aren't as handy to use.