Running Debian Testing Squeeze recently led to me upgrading my system (apt-get upgrade). Based on recent experience with all the performance problems from the intel graphics drivers I did a glxgears check before upgrading which gave me a result at about 1200 fps.
After upgrading from intel 2.3.2 to intel 2.8.1 graphics drivers the performance suddenly dropped to 200(!!) fps! Something was definetively wrong.
The solution:
Upgrade your kernel! I was running Linux Kernel 2.6.26, update it to the 2.6.30 kernel which is available via the apt package system, and your fps should rise to ~500fps. Definetively helped me :) Will come back with more if I find something.
