It was last November that GNOME software rendering began working with the LLVMpipe driver after it picked up GLX_EXT_texture_from_pixmap support and other changes. The GNOME 3.x Shell began to work quite well on this CPU-based software graphics driver that uses LLVM to take advantage of modern CPU features like multi-threading and the latest instruction sets. There's still ongoing work to improve the Gallium3D LLVMpipe software rendering with initiatives like VGEM, but already for Fedora 17 they're looking at making the GNOME Shell on LLVMpipe the default fallback for those without GPU hardware acceleration.
For this GNOME Shell Software Rendering test-day, they're looking for anyone to help out regardless of CPU architecture, old CPUs, or video card. Those looking to help out or just to try out the latest Fedora 17 spin, visit this Fedora Project Wiki page. This test day is similar to their recent GNOME Shell test day and their common graphics driver test days. Regardless of being a Fedora user or not, it's good to help them out with these test days since their fixes and other contributions end up landing back upstream.