I think you're right, actually. There are occasions where you use a feature that's ostensibly supported, but it needs to be emulated by the driver in software (

I think you're right, actually. There are occasions where you use a feature that's ostensibly supported, but it needs to be emulated by the driver in software (I think geometry shaders might have been this way on some OS/hardware combination). This is where some of OpenGL's reputation for fast/slow paths comes from.