Intel Celeron, Pentium Haswell HD Graphics On Mesa 10.1-devel
The Reaction Quake 3 game is running slightly faster with Mesa 10.1-devel over Mesa 9.2.1 as found in Ubuntu 13.10 stable, but there was no change found for this Intel Celeron Chromebook with OpenArena.
Warsow and Xonotic saw no real change in performance out of Mesa 10.1-devel.
When really stressing the Celeron HD Graphics on Ubuntu Linux by running Xonotic with ultra quality settings, there was a sharp improvement in the frame-rate using the latest Mesa development 3D drivers.