for my 2x 290 cgminer is 2x faster but unstable, hope for new version of OpenCLMAX to match speed!
I have 2x 280x they are mining with 2x instances of the miner on 2 workers. Seem to be mining well. I have them undervolted whats interesting is they're running far cooler than when mining Script. ie, 68C instead of 75 - 80C