For anyone wondering whether the Mesa/Gallium3D drivers will work with the Humble Introversion Bundle titles (or are thinking about buying the collection at the last minute), here are the results from some quick tests using different hardware and drivers.
The Linux games from the Humble Introversion Bundle (including the bonuses) ended up being Uplink, Darwinia, DEFCON, Multiwinia, Aquaria, Crayon Physics Deluxe, and Dungeons of Dredmor. For the most part, these games work fine on the open-source Linux graphics drivers. But then again, these are all indie games and not AAA titles running visually-advanced engines like id Tech, Unreal Engine, or Unigine. Several of these multi-platform games are also several years old. The proprietary AMD Catalyst and NVIDIA Linux graphics drivers also work fine, as one would expect.
A variety of ATI/AMD Radeon, NVIDIA GeForce, and Intel (Sandy Bridge) hardware was tested on an Ubuntu 11.10 install with the Linux 3.2 kernel and Mesa 7.12-devel Git as of this morning using the default build options. Unfortunately none of these Humble Introversion Bundle games offer any automated benchmarking capability, so the amount of testing for each configuration was limited.
The Darwinia game from Introversion Software was officially released in 2005, so seeing this title run under modern Mesa/Gallium3D is not impressive. It worked fine across the Intel / Nouveau / Radeon drivers. The only other issue to note is that when changing the resolution / windowed mode with the Radeon stack, the game would crash due to a segmentation fault.
Uplink is another title from Introversion Software, but it is a decade old. One would think all of the bugs are worked out by now and that Mesa/Gallium3D would handle it just fine, but with the Git graphics stack used, it would crash on start-up when using Nouveau and Radeon (R600) drivers. Intel Sandy Bridge on the Intel classic Mesa DRI driver worked fine.