I finally did it. Everything went fine, except for the proprietary ATI/AMD fglrx graphics driver and the related x.org setup. To get suspend to work I had to upgrade to the latest fglrx driver. After this the UI felt pretty slow, much slower than it was before the upgrade. OpenOffice.org Impress was almost unusable, it took about 5 seconds for a slide change.
The problem consisted of two parts, one was that cpufreqd was slowing down my CPU. I didn’t have it installed before, so I removed it. I’m relying on the ondemand governor anyway. Then I also added the following options to the device settings in my xorg.conf:
Option "XAANoOffscreenPixmaps" Option "AccelMethod" "XAA"
No my X is as fast as before, I even gained a bit of 3D performance with the new fglrx drivers.
Suspend and wake up works also after I set the following options in /etc/default/acpi-support: