(I think you said to use max 14.7 but here's my report anyways for 15.x);
The 9.1 version has issues with some GPUs, i have my 290/390, my 380 and some random 280x get lowdifficultyshare errors for 100% of their hash. I tried the -a 3 option, it doesnt fix it.
Cheers.
Don't worry about it, by the time a updated linux version comes out the profit on this will be the same as ethash.