With there being much discussion about the Radeon image quality comparison, I've carried out the same comparison on the NVIDIA side using the Phoronix Test Suite image quality comparison functions in an automated manner just as used in the other articles.
These screenshots were captured from a Intel Core i7-based Lenovo ThinkPad W510 notebook with a NVIDIA Quadro FX 880M graphics processor. The Quadro FX 880M is based upon NVIDIA's GT216GLM core and has been supported by the open-source reverse-engineered Nouveau driver for some time. The latest NVIDIA Linux and Nouveau drivers were compared in today's simple tests.
OpenBenchmarking.org, you will be able to grab the raw data from there just as you can do right now with the performance results. Right now the image quality comparison uploads are disabled for OpenBenchmarking.org simply due to resource constraints with the associated overhead of storing many images rather than just textual data. Soon though when the new OpenBenchmarking.org infrastructure is rolled-out, IQC uploads will be permitted. The abstract result types comply with all other PTS/OpenBenchmarking.org features and capabilities. To see how your system compares to these NVIDIA/Nouveau visuals, you can simply run phoronix-test-suite benchmark nexuiz-iqc.
More Linux graphics image quality tests are on the way. In terms of how the Nouveau Gallium3D driver is currently performing against the NVIDIA binary blob, in Nouveau For Open-Source NVIDIA In Mesa 8.0 Is Mixed are the latest results as of mid-January across a spectrum of NVIDIA GeForce hardware. Also of interest may be Nouveau Reclocking: Buggy, But Can Boost Performance and Nouveau 2D Still Has Room For Improvement.