Phoronix had a very pleasant surprise over the weekend which was apparently also a complete surprise to the AMD Linux driver team; vastly improved GPU performance on the 3.12 kernel.
In tests on a dozen cards ranging from the elderly HD3850 to the HD6950 all cards showed at least some improvements and in some cases increases of 50%.
Keep your eyes tuned for updates as they work with AMD's Linux team to see where these performance increases originated from and to give Phoronix time to get their hands on new hardware for more testing.
I'm hopeful these benefits will follow towards the AMD 7000 and RX 200 series of GPUs, especially at higher resolutions.
If so, this would be an unexpected turn of events for SteamOS, AMD and Mantle. I wonder if the R9 290X without any additional GPUs might be able to run 4K at 40fps or more, at Max Settings in modern games like Metro:LL, Crysis 3 and other GPU-intensive titles. If so, it'll blow nVidia out of the water (at least on SteamOS).
More notable is that Intel - for the first time in it's history I guess - is slacking when it comes to linux support, both for CPUs and iGPUs. The only graphics card that is fully functional (and crazy fast) with linux kernel 3.12 for the moment is AMD. nVidia still has problems with kernel 3.10/3.11, and Intel - which has by far the largest group of linux graphics devs, over a 100! - hasn't been able to merge all the functions in kernel 3.12 yet, even though they have pretty good code in it already, it's not like it doesn't work like with nVidia, it works decent.