i finally got bitten in the ass, by this transition. actually, it was not the transition itself, but my great idea of removing the "not required" xserver-xorg-video-* libraries some time ago.
don't ask me, why, but i have removed xserver-xorg-video-ati and other dependencies back then. everything was fine until i have dist-upgraded and rebooted...
the result: because of the missing wrapper (xserver-xorg-video-ati was gone), the DPMS of the monitors were not handled correctly and i have lost my dual-screen setup on the desktop at work! (or maybe something similar was the issue)
to cut the story short: i have downgraded to xorg from stable for now, and hope that the transition will finish soon.