I'm not a free-as-in-freedom die-hard, but I know a bit about GL stuff, and Alan's comment doesn't make sense to me. The premise in Alan's comment seems to be that GLES2 is a low-level enough, universal enough interface to graphics hardware that you wouldn't in your right mind want any lower-level interface to it. Whence his "move the HDD heads" analogy.
That premise is really false, and the HDD analogy, just wrong. GLES2 is plenty high-level enough that you could reasonably want a lower-level interface to graphics hardware. Cases in point:
1) all GL implementations/drivers that I know have serious bugs that affect stability, security, performance, correct rendering, and memory usage of applications using them, and force serious applications to actively work around them. (I work on the Mozilla Gfx team and we have work-arounds in place for about every GL implementation we've encountered).
2) there exist competing APIs on the same level, especially Direct3D. They have the same issues as in 1).
3) there exists innovation in the area of establishing new interfaces to graphics hardware, either at the same level as GLES2 (e.g. GLES3) or on a lower level than GL's (e.g. Gallium3D).
I hope it's clear that these 3 points are valid reasons why anyone interested in graphics programming, let alone a driver developer, would be disappointed that any given flavor of GL is presented by a hardware vendor as the unique possible interface to their hardware.