If anything this shows what a placebo effect Windows 8 has been having on people who said "Windows 8 is better for gaming than Windows 7!". It's pretty obvious almost nothing changed.
As for the OpenGL drivers - let's just say Intel sucks at writing drivers. They have a decade of catching up with Nvidia and AMD. If even Nvidia and AMD drivers are not up to par yet because they haven't put too many engineers (or the best of them) on those OpenGL drivers, you can imagine it's even worse in Intel's case, where they have that much less experience writing drivers for the latest OpenGL 4.3 features.