I am kinda new at the whole GPU mining. I am running Ubuntu 14.10 headless and the most I can squeeze out of my R9 280x is 68 MH/s. I set gpu-miner -s 10 -c 1 which got me to 68, before I was at 65. My card is fully stock. Can someone please post what you have your core/memory set to. I'll figure out the commands to set it.
That sounds about right for that card. The people who are mining faster are using custom software - we'd release it if we could, but we don't have the software ourselves.
We're working on optimizing things.