This does not work. I mined with constant speed for 24 hours and the returns were only a quarter of what they claimed. Expect a 4th of what it says.
Works well for me. I have one r9 290X and one r7 260X, using cgminer from 1gh, I'm seeing about 605 MH/s, the calculator says I should be getting 9.0039 MAX per day at current difficulty of 126,116 and 9 MAX is indeed what I'm getting. Actually, a little less than 9, because whenever I'm sitting at the computer I do
aticonfig --od-enable
aticonfig --odsc 800,650
to turn the 290X's fan down from jet-taking-off to kitchen-stove-fan, so I can hear myself think. This brings hash rate down to 520 or so. And then when I go away
aticonfig --odsc 1000,850
for normal speed of 600-640 MH/s.