I'm still using Ubuntu Dapper. Why? Because I don't want to mess a lot with this install and let a dist-upgrade trash it completely every six months or so. Trust me, I've done 2 or more dist-upgrades in Ubuntu and none of them went well.
Anyway, I am still running Dapper and I'm proud of it. The only problem with this is that firefox and thunderbird shipped with Dapper have become very outdated. I wanted to try the webmail plug-in, but it only works for thunderbird 2. Damn :(
Fortunately there are some kind people who also have an older Ubuntu install and created a script to easily install the latest versions of both firefox and thunderbird on any Ubuntu version. Cool eh :)
The script is called ubuntuzilla and you need to run it as root. Not as a regular user, not using sudo.
Use it at your own risk and make a backup of your mails before using the script!