The second Alpha release of Ubuntu "Precise Pangolin" is finally out a the latest stable kernel, a new Upstart, LibreOffice 3.5 Beta 2, Unity 5.0 and lots more.
Ubuntu "Precise Pangolin" Alpha 2
The next LTS release already comes with Firefox 10 but there's not need to upgrade to it if all you're looking for is a browser upgrade. Ubuntu 11.10 already has Firefox 10 at this time. It's a simple update away.
As usual check out the technical overview in particular the known issues section before diving in. It's always a good idea to have an idea what you're getting into first.