Bill de hÓra blogs about how the change to Ubuntu went and how it is working today
Most of this was written back in September. After about 6 weeks of heavy use, there's nothing that has me wanting to move off Ubuntu. It's remarkably solid and well-designed, and maybe no more than 2 years away from being something anyone could use. Definitely a keeper.
The only real downside are some applications I truly miss from Windows – these are Feeddemon, Copernic and TortoiseSVN which have been supplanted by Bloglines, Beagle and Subclipse for now. Beagle and Subclipse are fine, but not having a really good client side aggregator is a pain.