The ATI drivers after 11.6 have a bug that makes them consume 100% of CPU.
But drivers before 11.7 not work with kernel 3.0+
So I have found a patch:
http://eduard-x.blogspot.com/2011/05/amd-catalyst-115-2639-debian.html
and using 3.1 kernel and 11.6 drivers with this patch on Ubuntu oneiric.
Everything works fine (also spent full day to found this solution).