F16 Alpha ATI Radeon issues?

[Michael Schwendt]

In an F16 Alpha install done via an upgrade from F15 final, I get various
rendering issues in GNOME Shell, such as

  http://mschwendt.fedorapeople.org/tmp/screenshot-f16-alpha-damage1.png

Not always, but at random times. Also:
 - perceived lag (compared with F15)
 - areas of the screen not getting refreshed in time, staying blank
   until I touch the window or move a GTK slider,
   e.g. individual mailbox subject lines in Claws Mail summary view
 - once, a few large black rectangular areas have appeared around an
   xterm window when moving it above a pair of Emacs and Firefox
 - lines of output in gnome-terminal and/or xterm don't appear and
   are displayed only when moving the window or hitting Enter once more

Is anyone aware of such issues? Is it likely to be a driver issue or
specific to the GNOME Shell? (dunno whether trying out a different WM would
be a sufficient test)

http://bugz.fedoraproject.org/xorg-x11-drv-ati
lists 177 tickets. Where can I find a guide on how to report
"the right stuff"?