There isn't too much that's exciting about Mesa 9.1.6 since the stable series is only about shipping bug-fixes in point releases. However, there is a wide assortment of bug-fixes. Among the bug-fixes for Mesa 9.1.6 include addressing a Wayland EGL platform crash, rendering artifacts in VDrift and SuperTuxKart, broken compilation on LLVM 3.3, VDPAU not working on a hybrid laptop with DRI_PRIME, and a HiZ Heroes of Newrth corruption problem.
The list of known bugs that were fixed in Mesa 9.1.6 can be found via this documentation commit. The Mesa 9.1.6 source packages are available from this FreeDesktop.org directory.