I have been trying to limit the software that I install on my laptop running Ubuntu to that which is available in repositories, as opposed to manual installs or building it myself. The main reason, is it is a hassle to keep up to date as software changes.
I was holding off installing the Firefox 3.1 beta, as I thought that I would have to download and manually install it. This page describes the repository that has the latest Firefox 3.1 beta. Once I configured that repository, all I had to do is run
sudo apt-get install firefox-3.1
Everything is working great with this version of the browser, except that Google Gears is not compatible. This just means that I will not be able to use the offline mode of several sites. If I need that, I can always revert bact to Firefox 3.0.x.