Phoronix published a review on the AMD Linux Graphics: The Latest Open-Source RadeonSI Driver Moves On To Smacking Catalyst

A quote from the article:

Following this weekend's Radeon R9 Fury open-source Linux driver tests with the DRM-Next code to be merged into Linux 4.3, the latest Mesa 11.1-devel Git code, and LLVM 3.8 SVN for the AMDGPU compiler back-end, I proceeded to run some bleeding-edge open-source Radeon Gallium3D graphics versus AMD Catalyst Linux benchmarks on Ubuntu.

This Linux 4.3 DRM / Mesa 11.1-devel (Git master) / LLVM 3.8 SVN open-source stack was compared to the Catalyst proprietary driver. Originally I was going to use the latest Catalyst 15.7 driver release, but its kernel module was running into issues on this Intel Skylake-based system used for testing on Ubuntu 15.04. Thus I resorted to using the packaged fglrx 15.20.2 / OpenGL 4.4.13374 OpenGL driver as packaged in Ubuntu Vivid that would play fine with the Skylake system running Ubuntu with the Xfce desktop.

 AMD Linux Graphics: The Latest Open-Source RadeonSI Driver Moves On To Smacking Catalyst @ Phoronix