Note in 2.7x there was no support for using OpenSubdiv on the CPU at all, it was purely for viewport rendering as an option.
The idea here is to use OpenSubdiv for everything, which has some new challenges. There are things that Blender subdivision does better than OpenSubdiv, particularly dealing with non-manifold topology and UVs, and quickly updating on topology changes in edit mode.
Once the existing functionality is replaced well enough better creasing can be looked at.