Urban Terror also runs fine with the open-source drivers. The Gallium3D drivers here are dramatically faster -- almost twice as fast for R600g -- than classic Mesa. The Gallium3D drivers reach around 60% the speed of the Catalyst blob in this ioquake3-based environment.
The results are not very different at 1920 x 1080. Of course, if Swapbufferwait and other non-standard tweaks were made, additional performance could be tuned out of the open-source driver stack, but still it would be no match to Catalyst.
The ATI Gallium3D drivers are certainly making progress in improving the performance and are definitively better than the classic Mesa drivers, but they still have a ways to go to performing closer to the official Catalyst Linux driver not only in terms of performance but also features and OpenGL support level.
These test results are also available on OpenBenchmarking.org for comparisons, etc.