I'm rocking various (Sapphire, XFX, Gigabyte) 270 & 270X and am getting 2.05+MH/s! 
Settings:
With previous software I was using 2 threads with other settings than above, but with the optimized x11mod and after a LOT of testing the past couple days that's the "best" I have so far. I can push it faster but that seems to be pretty stable across all 5 of my machines (27 GPUs, > 50MH/s). If anyone has any better settings for 270's please pass along
Settings:Code:
"gpu-threads" : "4",
"gpu-fan" : "75-100",
"gpu-engine" : "1200",
"gpu-memclock" : "1200",
"gpu-powertune" : "20",
"kernel" : "x11mod",
"temp-target" : "75",
"temp-overheat" : "88",
"worksize" : "64",
"shaders" : "1280",
"thread-concurrency" : "6401",
"rawintensity" : "32768"
"gpu-fan" : "75-100",
"gpu-engine" : "1200",
"gpu-memclock" : "1200",
"gpu-powertune" : "20",
"kernel" : "x11mod",
"temp-target" : "75",
"temp-overheat" : "88",
"worksize" : "64",
"shaders" : "1280",
"thread-concurrency" : "6401",
"rawintensity" : "32768"
With previous software I was using 2 threads with other settings than above, but with the optimized x11mod and after a LOT of testing the past couple days that's the "best" I have so far. I can push it faster but that seems to be pretty stable across all 5 of my machines (27 GPUs, > 50MH/s). If anyone has any better settings for 270's please pass along