Windows 10, Nvidia GTX 1080Ti
Broken: Blender 2.78c
Short description of error
Creasing strength is strongly inconsistent between the Cycles adaptive tesselation and plain subsurf (with or without OpenSubdiv).
Exact steps for others to reproduce the error
Open attached .blend, press shift-z or f12
Both cubes have a creasing value of 0.3. The left one's subdivisions are set to 5, and adaptive tesselation is locked at max 5.
The cubes should be identical in this situation.