Ubuntu 6.06 (Dapper Drake) is out on 1st June 2006.
Here are the simplified instructions for upgrading from 5.10 (Breezy Badger)
The instructions for this are not very clear to the uninitiated so here is a simple version:
- Open a console as root.
- cd /etc/apt
- chmod +wr sources.list
- emacs sources.list
- replace all references to breezy with dapper
- If you want non-official packages uncomment the universe lines (remove the # characters)
- save and close emacs
- sudo apt-get update
- sudo apt-get dist-upgrade
Wait and then you have a Dapper Drake system.
Developer Rants 
Thanks – this is just what I had been wondering! Is it possible to restore to Breezy, if I don’t like Dapper? Do you think that it’s not very likely that I’d want to go back to Breezy?
I have only just updated to Dapper from Breezy so it’s too early so say. However the Ubuntu team do such a great job you are unlikely to get any problems at this late stage!. I typically wait until a week before the release date before upgrading.
If you wanted to revert I guess you could change the links back – and dist-upgrade again. However I have not tried that.
Um, this method is considered bad, though harmless if you’re the only person on the computer. It’s better to edit sources.list as sudo’d root.