The main new element of this OpenGL drivers status is the introduction of the open source Mesa drivers for Intel GPUs on Linux.
Outside of the amazingness of the initiative, we can't really say that the quality is here. The overall level of quality just based on the OpenGL samples is below the other implementation but it's remain close. Particularly, the geometry shader is not usable with Mesa.
Only OpenGL 3.2 and OpenGL 3.3 samples are tested but Mesa supports even some OpenGL 4.4 features. The issue is that Mesa is essentially making progress on a per-extension base not on a per-version base which doesn't match how the OpenGL samples are written.
I definitely need to study more the Mesa implementation and I actually have a strong desire to build my own from source and maybe implement some stuff for fun if I manage to find the time.
Despite the mix results, it's still better than what I was expected and considering the evolution of the software ecosystem, it will pay off eventually. I would not be surprise if the implementation had a better feature set support than Apple already (There is KHR_debug support and it's working fine!). Quality will follow and performance... it's too early to say.
The other main evolution since the previous OpenGL drivers status is the released by AMD of OpenGL 4.4 drivers. The OpenGL 4.4 features are pretty broken up but the rest of the drivers received serious bugs fixing.
I can't exclude that there isn't bug in the samples, so don't hesitate to open an issue.