Im having 760 kh/s at 7970 (< 0.3% rejects) (which is same as 280x) using config which can be found on this page
http://cgminer-config.com/. I've made that page a while ago so people could share theirs configs and vote for best ones ;P
That config is crazy imo. GPU fan at 95% is a big no-no for me. The fan on my hottest card run at 55% for 82 C.
On topic: Really large amounts of unexchanged building up now
