Intel's Ian Romanick submitted their Mesa 8.0.4 results for Intel Sandy/Ivy Bridge GPUs about one month ago with the OpenGL ES 2.0 conformance test results to the Khronos Group. 30 days have passed without objections so their review period has cleared. This means that Mesa in conjunction with this Intel hardware is officially conformant to the Khronos GLES 2.0 specification.
"Not only is this great news for my team at Intel, but it's terrific news for Mesa. Mesa has had a long history with OpenGL, the ARB, and Khronos. This is, however, the first time that Mesa has ever, in any way, been listed as a conformant implementation. This is a big boost to Mesa's credibility," as said on Ian's blog.
Now to get working on OpenGL ES 3.0 support, which they hope to have mainline in Mesa by early next year.