As a new AMD fanboi I feel compelled to post this.
Despite what we might have expected going in, the AMD Radeon R9 Fury X actually scaled in CrossFire better than the NVIDIA GeForce GTX 980 Ti. This comes not only in terms of average frame rate increases, but also in lower frame time variances that result in a smoother gaming experience. In several cases the extra scalability demonstrated by the Fury X allowed its dual-GPU performance to surpass a pair of GTX 980 Ti cards even though in a single GPU configuration the GeForce card was the winner.