Getting started with Doom 3, the low-end GeForce GT 220 was the only graphics card where when comparing the Nouveau vs. NVIDIA driver clock-for-clock was there any competition. When the GeForce 9800GT was running at the same clock speeds with the binary blob as it did with Nouveau, it was 66% faster using the official NVIDIA software. The GeForce 9800GTX at the same clock speeds meanwhile was 69% faster than Nouveau.
For the open-source Nexuiz game there is still a large performance disparity between the open-source Nouveau driver and the closed-source NVIDIA Linux binary driver.
The GeForce GT 220 can compete fairly well on Nouveau against the NVIDIA binary driver when both drivers are running the GPU core and video memory at the same frequencies, but this is a very low-end GPU and is still about 69% slower than where the hardware is rated to run at with its optimal frequencies.