So I just got my ASUS R9 290, plugged it, couldn't get it to run properly with cgminer so I switched over to sgminer.
I undervolted my card to 1.023v, and it's stable, hashing at 800 kh/s with 911/1250 and 75c.
Thing is, my WU is a lot higher than my KH/s (I know WU is what counts), is it okai? It's stable on 1k WU with 0 HW.
Actually, WU usually levels out to ~0.9 what your KH/s is. If you're running 800KH/s, you should be getting a WU:~720. Of course, this is all random, and sounds like you've had a stretch of good luck!
When we reboot our rigs, we notice massive swings in the WU until they eventually level out. We've seen as low as 500, and as high as 1200 per GPU. They eventually even out, tho.
Come back in 48 hours, and see what it says.