While Gallium3D is still in development, it's stabilizing quite well and the Radeon Gallium3D driver is out-performing the classic Mesa driver though it's not yet outperforming the Catalyst driver. The Nouveau Gallium3D driver, which is the first open-source 3D driver for NVIDIA graphics processors, is also working fairly well. Of course, you can check out our many Gallium3D articles and news postings for other details on the drivers and state trackers, if you haven't been staying up-to-date with our frequent information.
Being dropped inside the xorg-edgers PPA is now Gallium3D drivers for Intel, ATI, and NVIDIA. This is different than the Gallium3D support found in earlier PPAs as the Intel and NVIDIA drivers have been added and a libgl1-mesa-dri-gallium package has been introduced, which makes it easier to switch to/from the classic and Gallium3D drivers. The Mesa stack has also been updated against the 7.9-devel code-base as of the 22nd of April, so it's also nice and fresh.
This work was announced by Tormod in our forums, which is one of the Ubuntu X contributors, and makes our forums one of the places you can go (along with all of the other developers and testers that are there) if you run into any problems once tossing in ppa:xorg-edgers/ppa and updating your graphics stack. For those just interested in trying out the NVIDIA Gallium3D and kernel mode-setting support, an easy way to do that is by trying Fedora 13 as even their LiveCD ships with the Nouveau (classic Mesa for old hardware, Gallium3D for all non-vintage ASICs) by default.
By the time that Ubuntu 10.10 (codenamed the Maverick Meerkat) rolls around in October, hopefully we will find at least the R300g (ATI's Gallium3D driver for R300-500 hardware, up through the Radeon X1000 series family) and the Nouveau driver become part of the Ubuntu stack to provide a more pleasant "out of the box" experience.