I'm testing the AMDGPU-PRO Beta driver (16.20.3) on Ubuntu 16.04 by running some OpenCL tests. The most significant issue I've noticed is that only ~680MB are available out of the 4GB of a Radeon R9-Nano. Given that only 1/4 of that can be allocated using a buffer object this proves quite restrictive.
In addition, I've observed some performance issues comparing with the fglrx 15.302.
I am seeing the same issue with the R9 380s...memory bug was fixed, but only showing 14 CUs, and clock is capped at 555mhz regardless of what is set in the card BIOS.