I wouldnt know, and I agree with shining knight. When I realized how hard it is to learn an API i figured "Hey, Ill make my own, and then Ill know it because I made it!" I looked into it and uh.. I decided to learn OpenGL. So unless you have ALOT of time on your hands, and acouple years, around 2- 6, I suggest you just learn OGL or D3D. But, if you do make an API, and its easy to use, I would be interested in using it.
"I''''ve sparred with creatures from the nine hells themselves... I barely plan on breaking a sweat here, today."~Drizzt Do''''Urden
If you want to make creating a GUI in OpenGL easier, just write a library that calls OpenGL itself, but has "button," "cursor," "checkbox," and similar classes that handle the low-level details. But don''t try writing an API. You''d be wasting your time.