Not sure if bugs of experimental features such as adaptive displacement are "allowed" to be reported here but I don't see how to let you know otherwise.
Here is one case which renders very strangely by this feature, then a box-shaped culling is occurring:
I found out that it must have to do with the mode of shading being applied to the mesh. With flat shaded surfaces it fails, for smooth shading the culling disappears.
Here is the .blend file:
Tested with official release and buildbot build from yesterday, both for Windows.