A crude test I performed involved opening ten tabs from the same links in my iGoogle RSS feeds section. While opening the tabs in Firefox 2, I wasn't able to click and view the tabs which have already loaded. In Firefox 3, I was able to do so with almost instantaneous response from Firefox.
UbuntuGeek posted some instructions on how to install Firefox 3 beta in Ubuntu Gutsy Gibbon. These were the instructions I followed after downloading the beta release since the following codes did NOT work for the Firefox install.
# tar xvzf package.tar.gz (or tar xvjf package.tar.bz2)
# cd package
# make install
Installing Firefox 3 beta on my Debian Box:
*Note: The steps are for Ubuntu - they worked on my Debian Box
#sudo apt-get install libstdc++5
Make a backup of old firefox preferences
#sudo cp -R ~/.mozilla ~/.mozillabackup
If you haven't already, download firefox 3.0b3 from HERE
Now you have the firefox-3.0b3.tar.bz2 file
Unzip the .tar.bz2 file in /opt directory using the following command
#sudo tar -C /opt -jxvf firefox-3.0b2.tar.bz2
Link the plugins using the following command
#sudo ln -s /usr/lib/mozilla-firefox/plugins/* .
Create a link to your new firefox launcher using the following command
--divert /usr/bin/firefox --rename /usr/bin/firefox
#sudo ln -s /opt/firefox/firefox /usr/bin/firefox
--divert /usr/bin/mozilla-firefox --rename /usr/bin/mozilla-firefox
#sudo ln -s /opt/firefox/firefox /usr/bin/mozilla-firefox