With QGears2 and using the X Render back-end, the open-source code led to a slightly higher frame-rate over using the official Catalyst driver in Ubuntu 9.10.
Compared to the X Render Gears test in QGears2, the text operations were substantially faster and about two and a half times faster than the Catalyst 9.10 driver with its X Render acceleration.
The performance with the image scaling test was close between the four test configurations.
From the three different test profiles we used and the two graphics cards that were tested, nearly every time the open-source driver stack wound up being faster than the Catalyst 9.10 driver. Past tests of other graphics cards and drivers have shown the 2D performance to be better on the open-source side, albeit these 2D tests are not very real-world representative (nor do they reflect the CPU usage) and on the 3D side the proprietary Catalyst driver is significantly faster and more feature-rich than the current open-source code. Anyhow, to see how these two drivers compare with your hardware, try out the Phoronix Test Suite.