Yesterday morning, I gave a presentation at the 2015 OpenFabrics Software Developers' Workshop. I discussed the status of libfabric support in Open MPI.
Here's a copy of my slides:
In short, the Open MPI development master (what will eventually become v1.9) contains two different plugins that use libfabric:
The two plugins (currently) target different networking hardware, and use different portions of the libfabric API. As such, these two plugins provided excellent feedback to libfabric, in an MPI-libfabric co-design sense.
There's still much work to be done in libfabric, but having a real, production MPI implementation using libfabric in multiple different ways has been extraordinarily useful.