Some speed comparison:
Please don't remove standart bleder's subdiv. I don't see any advantages of OpenSubdiv. I was hoping that the Opensubdiv will give a more rounded geometry
or more optimal creases, but i don't see any difference, and I am disappointed :(
OpenSubdiv is not for giving more rounded geometry, it's mainly giving better performance (see http://code.blender.org/2014/05/opensubdiv-gpu-tessellation-wip/). It's also still WIP.
Anyway, can confirm some weirdness here.
Steps to reproduce based on .blend from above:
Will move to a TODO now. We've got viewport project happening now, and with bumped OpenGL requirenment we can enable tessellation shaders without too much hassle. Wouldn't spend time trying to solve the issue before we've got updated OpenGL pipeline, it'll be just pointless.