I understand its known for its 3D power, so I dont know how it fairs in the 2D realm. From what I see, its better than GTK+ and all these other 2D graphics.
Anything that can be used for 3D graphics can also be used for 2D graphics. It's just a matter of drawing a 2D scene instead of a 3D one. So yeah it works quite well.
If you want a simplified interface for 2D graphics, I often recommend SFML ( http://www.sfml-dev.org ). It uses OpenGL, but provides an API that's simpler and more intuitive for 2D graphics.