Depends on which reviews you cherry pick, most others have it 20 to 30% faster than a 980TI.
TPU make a big thing about it being 13% faster with an 11% overclock, so from 100% they are getting 120%, right....
Again most others say about 5% to <15% from a 15% overclock
Compared to some older 980TI overclocked benchmarks there is only a sub 5% difference and the 1080 doesn't clock anything like as well as the 980TI.
Reviewers and enthusiasts a like will take from all this what they want.
The facts are its not a all clear cut thats its this amazing world changing super GPU that all the hype is about.
Really its just a typical upstep in performance, and actually a bit 'meh' considering its 16nm vs 28nm, and then there's the price, very much inline with all the hype, only the hype is not warranted, not by a long shot.