For the old OpenArena 0.8.5 game that's not too demanding, there isn't much net change between Mesa 7.9.2 and 8.1-devel -- only 18% over two years. However, it looks like there might be some syncing issues with the perfect 120 FPS average. Swap buffers wait was disabled during testing and the Phoronix Test Suite automatically sets the vblank_mode to 0, but for some reason it looks like OpenArena 0.8.5 on the recent driver code isn't honoring this for the particular game. Mesa 7.10.3 was up at 141 FPS.
The newer OpenArena 0.8.8 release also faces a similar problem to the older version.
For World of Padman, a game based upon the same engine (ioquake3) as OpenArena, the performance from Mesa 7.9.2 to 8.1-devel is up by 84%.