The open source drivers that come with Ubuntu 10 and 11 work perfectly well but don't do 3d acceleration.
The ATI proprietary drivers installer completely hosed my system which took a morning to reinstall.
As of Tue Mar 22 2011.
I'm rating it 3 overall because although video works fine, I'm only getting half the functionality (no 3D). My graphics card in 2003 had more kick.