Just got to use this with my r9 280x and love it!! Getting about 200 sol/s.
Old 280x cards with claymore's miner(and I think with optiminer's miner too) can show more better results - up to 325 sol/s with modded timings.
It's true. With 12.5 Claymore I have on my 280X 330-335 Sol/s with modded bios, overclocked memory and downvolted core.
Optiminer gives only 275-300 Sol/s.