OpenGL is a dog's breakfast of an API. It's everything an API shouldn't be -- stateful, verbose, and committee-driven. Just take a look at Valve's .PDF.

An OpenGL programmer spends a large part of his/her time trying to maintain a mental model of the underlying driver's state and behavior. And God(s) help you if you step off the path used by popular applications and game engines. You can expect combinatorial bugs out the wazoo, again because the API and driver layers are so stateful.

I agree with the grandparent -- it's well past time that a D3D-like API was adopted by other players. I've used OpenGL since the Quake 1 days and I've never understood why so many people sing its praises. The days when D3D was an inferior API are more than a decade behind us.