I do have to say that my experience between the OLDER fglrx driver (for an R9 285 card (GCN 1.2)) and the mesa 13/13.1 releases (amdgpu driver) has been that th

I do have to say that my experience between the OLDER fglrx driver (for an R9 285 card (GCN 1.2)) and the mesa 13/13.1 releases (amdgpu driver) has been that the fully open stack is MUCH MORE STABLE. It isn't perceptibly slower, but it is a lot less likely to have some weird corner case bug in random games.