I know SFML-2.0 quite well (Don't go 1.6, it's a few years old, 2.0 is very stable and has loads of nice features), and I must say, it's far better than what I tried to do with SDL.
The benchmarks are actually a bit one-sided, because they were done on pure SDL I think, which uses CPU rendering instead of the GPU. However, when equally matched (both use GPU rendering), SFML is still faster.
Not only that, but SFML is OO, which is really comfy.
One annoying thing that I fixed in SFML is that it isn't really made for passing window control to different threads. The OpenGL rendering contexts are not deleted, which results in a memory leak. They're not deleted because SFML can't know when a thread dies according to Laurent Gomilla.
SFML-2.0 works perfectly with OpenGL, if you want you can use SFML as a window manager, sound manager, and directly call openGL commands. In fact, SFML includes an OpenGL.hpp (located in SFML/OpenGL.hpp), which is a correct version you can include. It works very well, once made a little 3D area where I moved around.