Originally Posted by lloeki
e.g I get ~2-3k with a radeon 9000 on both a PIV 2.6HZ and a pII 450mhz.
Erm all that your example means is that the glx frame rate is purely limited by the video card. Likely fill rate or there abouts.
While glxgears isn't a benchmark that you can directly say "since I get more FPS than your machine, my computer is better at games than yours is", it is still definitely representative of the throughput of the video card.
On a well-configured system with the specs of the first post, the frame rate should probably be around 20,000. At any rate, no where near as low as 2500 as shown in the first post. I have an 8800GTX with Core 2 Duo 6850, and I get 23000 - 24000. I don't use Compiz or anything like that.
My suggestion is to definitely look into what has changed. Perhaps the only difference in the system is that a 3D compositing window manager is running, slowing down any program like this.
The important question is still: do real games run okay? Try the demo of ETQW perhaps. While the full game runs a bit better for some people, this is a "real" situation where the performance of most parts of the computer will be tested.