A change to the version numbering convention for the Mesa releases was proposed and accepted as well. Rather than having the odd numbered releases be the development versions (i.e. Mesa 7.1 and 7.3) and the even numbered releases being stable (i.e. Mesa 7.2 and Mesa 7.4), the first release in each release stream (such as Mesa 7.5.0) will be the "development" release while the next minor version (such as Mesa 7.5.1) will be the version that is more tested and contains additional bug fixes and should be stable. While a lot has been going on within the Mesa community, the first release candidate for Mesa 7.5.0 is now available.
The single biggest change in Mesa 7.5 is the mainlining of the Gallium3D driver architecture. Gallium3D is now developed within the mainline Mesa code-base, but still this much-improved driver interface is not yet ready for the public limelight. The Gallium3D drivers for Intel, NVIDIA, and ATI/AMD hardware are still lacking, but as the year moves on we should see more improvements in this area.
Gallium3D is designed to make driver development easier and more effective by being able to write a "simple" driver that interfaces with Gallium3D and then the generic state trackers target a unified API where any driver can then access the OpenGL support and other features. An OpenVG state tracker was recently released, there is an OpenCL state tracker due out this summer, and a shader-based video decoding interface also in the cooker.
Besides the integration of Gallium3D, Mesa 7.5 introduces support for the following OpenGL extensions: GL_ARB_framebuffer_object, GL_EXT_vertex_array_bgra, GL_NV_texture_env_combine4, and GL_EXT_texture_swizzle. These new OpenGL extensions are present in the software-based Mesa implementation, but if you want hardware acceleration they right now can only be found in the Intel driver.
Other new work in Mesa 7.5 include reworked two-sided stencil support via GL_ATI_separate_stencil and GL_EXT_stencil_two_side and OpenGL 2.0. Specific to those using SPARC-based hardware, there are various Assembly optimizations. Lastly, Mesa 7.5 has initial support for separate compilation units in GLSL compiler.
The Mesa 7.5 Release Candidate 1 announcement can be found on the Mesa development list. The source code to this newest release can be found in the Mesa3D.org beta directory.