Originally Posted by semantics
really you mean the engine built just recently runs better then the old ass source engine, amazingly predictable. Do people not notice things like DX11 WoW runs faster then DX9 WoW because WoW doesn't use crap like tessellation, the game is visually identical, just changing to DX11 code path caused a significant performance boost because DX11 is not ancient and was designed to have less overhead.
Valve isn't using latest OpenGL neither. I think they are using the equivalent to DX9 which is OpenGL 2.1.
Latest version is OpenGL 4.3.