I have not noticed any appreciable change in hashrate.  The only difference I have seen so far is that the auto-adjusting fan speed is now higher.  Before my fans were running at like 45%, now they're running at 75%.  So, I guess you could say slightly higher power usage in return for keeping the chips a couple degrees cooler which theoretically might help with long-term reliability.   BTW, I run mine in performance mode, so your results may differ if you run yours in one of the other modes available.