Bleeding edge browsers and web developers take note, for the latest Firefox 3.5 (previously 3.1) beta is in the wild. There doesn't seem to be much that's entirely whole-cloth new to this release, except perhaps the undo closed window feature. The release notes have more detail on the latest test release, and users, as always, shouldn't expect all their extensions to work in this version. Trying it out already and liking what you see? Were you expecting more? Tell us how 3.5b4 comes across in the comments. [Firefox 3.5b4 Beta]