LLVMpipe is in effect the modern software rasterizer for running OpenGL on the CPU in cases where there is no physical GPU or supported graphics driver available or for graphics driver developers wishing to debug an OpenGL issue in a neutral environment. LLVMpipe is much faster than Gallium3D Softpipe and Mesa's classic "swrast", but still it's a far cry from an actual GPU and proper GL driver. LLVMpipe is faster largely through its use of LLVM and is able to take advantage of multiple CPU cores and instruction set extensions like SSE3/SSE4.
In a new FreeDesktop.org bug report, Adhemerval Zanella Netto of IBM is requesting Git commit access to Mesa. His reasoning for working on Mesa is "working on porting the llvmpipe gallium driver to PPC."
So if you happen to be a PowerPC user without any graphics support, things may get better through Gallium3D optimizations for the CPU architecture. With a bit of luck, maybe we will see some overall optimizations and improvements to LLVMpipe as a result of this work.
Sadly though I still haven't seen any ARM optimization work yet for Gallium3D's LLVMpipe by Linaro or other ARM Linux stakeholders. Linux on ARM continues showing progress in new form factors, but for enthusiasts and those tinkering with the hardware, the ARM Linux graphics drivers remain a pain point. But, of course, open-source GPU hardware drivers would be the best case scenario and not all Linux users want to toke on LLVMpipe.
We'll see what comes about with IBM's LLVMpipe PowerPC work, which will likely end up being a feature for Mesa 9.2 (or more likely known as Mesa 10.0) due to be released before year's end.