I don't know if this is true or not but, here's Quick Tip from Blender Today on Improving Open Subdiv performance #b3d http://blender.today/p/tutorials/Mrbbbc/quick-tip:-opensubdiv-performance
Use Subsurf with OpenSubdiv for all the objects in the scene, to keep high performance results.
(Even if you don't needed )
One or many objects without OpenSubdiv can slow down drastically other objects who will use OpenSubdiv. (depends by polygons, number of objects and hardware)
Also the number of subdivisions need to be set 1 or higher, to make use of OpenSubdiv.
And Optimal Display can improve the playback with some fps as well.