...and that Geometry Shaders (ok, and the questionable-quality v1.0 UVD/OpenCL hardware) is one of the few remaining features of R600 not yet supported according to http://xorg.freedesktop.org/wiki/RadeonFeature/
....and that this patch starts the last remaining big chunk of work before supporting OpenGL 3.3 (the highest version of OpenGL originally supported by the R600/R700 shipped) according to http://cgit.freedesktop.org/mesa/mesa/tree/docs/GL3.txt
...and that this web site has repeatedly shown good performance from that driver.
...and the question as to why if you are so worried about having cutting edge graphics features, you aren't already upgrading your GFX card every five minutes, like most PC gamers seem to.
...I think I can see why you are concerned . At this stage, though, I'm far more worried that adding feature XXX that I don't need or use, use will break/degrade/change something that already works.