I too have noticed performance issues with this new driver.
I ran "Scientific" benchmarks using Quake 4, UT2004, and Doom3, and with the previous drivers, I got these results:
AMD X2 4400
2 GIGs Ram
GeForce 7800 GTX PCI-X
Arch Linux Using Stock 2.6.16 kernel
1600x1200 - 54 FPS
1600x1200 - 72 FPS
1920x1200 - 83 FPS
1600x1200 - 24 FPS
1600x1200 - 48 FPS
1920x1200 - 53 FPS
Using the CK Kernel, there was some improvements in the "feel" of the game, but the FPS was smiler.
So, there is some differences between the driver versions.
Thats not even with Composite Enabled. With Composite, subtract about 10 fps from each of the new driver scores (Plus other issues).
Still patiently waiting for a bug fix release