Comment 232 for bug 509273

Neither radeon.modeset=0 nor modeset.radeon=0 would do the trick, the kernel modesetting somehow gets enabled.

Off-topic:

This LTS edition is not different from my previous experience. Somewhat more stable than the koala, like pulseaudio finally works without breaking every minute. The boot-up time in my case is doubled (about 2 mins), whence in feisty fawn it was just 30 secs. I understand I get some services to start which take time - I do not see what is going on, no system messages are shown. Maybe it can scare a user? So it was turned off. Probably, the stability does not necessarily depend on the window's buttons position

I hope, other people are luckier.....
I am optimistic though!