Will never understand why Ubuntu and friends don't just download Firefox, extract, create a shortcut to launch. Two minutes of work and you have Firefox that autoupdates when Mozilla releases. No need to add yet another PPA to the million and one that already exist.
Mozilla/5.0 (X11; Linux i686; rv:2.0.1) Gecko/20100101 Firefox/4.0.1 ID:20110413222027
Or why they don't use Iceweasel like Debian does.
$ apt-cache policy iceweasel
*** 5.0~b3-1 0
experimental/iceweasel-5.0 i386 Packages
experimental/main i386 Packages
unstable/main i386 Packages