Re: Hmm.
Having tested both on Ubuntu 14.04.4 and 15.10 I can say to you that you will have not only one but two wonderful ATI drivers.
On many steam games I get now 60+ FPS with both RadeonSI+Mesa 11.3git and AMDGPU (catalyst replacement) drivers on a stock R290 with no glitches whatsoever.
The future looks bright indeed.