Firefox 8 arrives with extensions off by default, Twitter search, and lots of improvements sprinkled all over. Going over the release notes, it doesn't look like anything major was included this time around but the complete list of changes is pretty hefty as usual.
Tab animations got shoved back due to regressions. Sad.
Ubuntu 11.10 looks like it hasn't received the update yet, but it should arrive by tomorrow if the updates back in Ubuntu 11.04 is any indication.