upgrading my kubuntus to Gutsy was a breeze. Not a problem at all.
* One old laptop with Crusoe 750MHz, SiS video and 300MB RAM;
* Celeron 2.6 GHz at work, SiS video again, with 1.5GB RAM;
* Core2 Duo at home, Intel video, 2GB RAM;
* AppleTV (nvidia video, 256MB RAM?)