Firefox 8 has hit the streets, and if you can not wait to get it up and running on your older version of Ubuntu, then you can run these commands at a prompt to get Firefox installed and running on your Ubuntu PC.
sudo add-apt-repository ppa:mozillateam/firefox-stable
sudo apt-get update
sudo apt-get install Firefox language-pack-en language-pack-en-base
There are a number of enhancements that have been added to Firefox 8. Twitter had been added to the search bar and there is more support of locals. Firefox should also be even faster and more responsive.