Nouveau: 24.86 seconds
NV: 40.78 seconds
Which is a 64% improvement over the existing Nvidia sponsored nv driver.
This is a very limited 2D only test and does not represent 3D performance but it does show that the developers are making good progress.
The Nouveau driver is quickly gaining support within the various distros. Fedora 7 shipped with an alpha version of the driver and Ubuntu has committed to assisting and supporting the project.
Nouveau Driver Homepage
To better show the improvements here is a benchmark comparing the free NV driver to the closed source Nvidia driver: NVIDIA Xserver driver Benchmark
In this benchmark (using a GeForce2 MX) the closed source Nvidia driver has a performance gain of 36% over the free NV driver. As Nouveau driver had a 64% improvement it even exceeds the Nvidia driver.
These figures should not really be treated as equal as they are using completely different Nvidia drivers. (6xxx series to hopefully the new 9x or 10x drivers.