I haven't had enough time testing it , but wit the current ccminer v7m7 , the results with the XCN are not so well. Its about 10MH/s but it should be twice better - my opinion...
twice would be a lot... knowing that a 780ti does only 14mh/s
You can get already a little more by overclocking the memclock of the p2-state to its maximum with nvidia inspector (which is 3500mhz and correspond to the nominal memclock value).
I will publish soon an update to use better launch parameter for the 980 (because for the moment, it just picks those of the 750ti), my 980s are doing around 12.5MH at the moment...