ATI Radeon OpenSource drivers on Debian or Ubuntu

By default Debian/Ubuntu LInux choose the best drivers for your ati radeon, but i wanted to know how the proprietary fglrx would worl so i gave it a try...
Result? ... a lot of glitches...

Here is how i returned back to the fine working ati opensource drivers with OpenGL acceleration:

sudo apt-get remove --purge fglrx fglrx-amdcccle fglrx-dev
sudo apt-get remove --purge xserver-xorg-video-ati xserver-xorg-video-radeon
sudo apt-get install xserver-xorg-video-ati
sudo apt-get install --reinstall libgl1-mesa-glx libgl1-mesa-dri xserver-xorg-core
sudo mv /etc/X11/xorg.conf /etc/X11/xorg.conf.backup
sudo rm -rf /etc/ati