They use OpenGL instead of DirectX for hardware acceleration. Microsoft's obviously not going to do that; using DX plays to their strengths in every possible way, from what their developers and toolchain is already optimized for, to what's already rendering the entire desktop in WinVista/Win7... so it could even mean IE10 on Win8 tablets will be better on battery life than FF/Chrome. I'm not an expert on this, but DX is likely the objectively better choice for hardware acceleration on Windows -- the reason FF/Chrome use OpenGL is because they have to support other platforms IE doesn't, and doing everything twice in OpenGL/DirectX to get the best result on Windows while still supporting Mac/Linux has obvious downsides.