I've made few researches. (damn, sorry for misspellings but little drunk...) People here on forum are telling, that one some SDK U'll get better results, on others worse. Its TRUE. BUT, power, consuming by card will also increase, same temperature.
Been doing 380Mhash/s on 2.2 SDK or 2.4 SDK. Changed to 2.1 SDK and 395 MHash/s. But also was using 15 W more, as well as 5C more with 100% fan (74C @ 75%fan vs 79C @ 100%)(same clocks). After calculating additional profit from hashes - additional cost of power = the same. The adventage is lower temps on card, which means it will last longer.