3.13 vs 3.12 vs catalyst
The only interesting change is Pixmark Volplosion in GPUTest. I don't know if such a great improvement is due to the kernel, probably a magic commit landed in mesa in the meantime.
Stupid 1 minute edit limit, I missread the last graph: there is no difference between 3.12 and 3.13.
3.13 has a lot of really neat stuff -- one of the thing that excites me the most is dynamically power off dGPUs on hybrid laptops (yay battery life!) -- but so far I haven't seen that there's much in the way of performance improvements.
I should compile linux-next and see if there's any improvement with the mobile SI chips, as there seems to be focus on that from what I've seen.