The difference in performance between the Founders Edition and these new AIB cards is actually quite small in comparison to Maxwell; it's only around 1-3% from what I can see. I've looked at a few reviews so far from Guru3D, KitGuru and of course OC3D, and the FPS gains are surprisingly insignificant. So what you are getting with ASUS, MSI, EVGA, etc is better looks (subjective) and superior thermals, which is where your own overclocking comes in because the stock overclocks aren't as impressive as they were for Maxwell. To illustrate that:
I won't post the images here as it may not be appropriate, but here is a review by Guru3D of The Witcher III at 1440p.
NVidia 980ti (reference) - 61 FPS
Gigabyte G1 Gaming 980ti - 71 FPS
NVidia 1080 (Founders Edition) - 82 FPS
MSI GAMING X 8G 1080 - 85 FPS
Another comparison, this time of GTA V at 1440P from KitGuru with their ASUS Strix 1080 review:
NVidia 980ti (reference) - 72 FPS
ASUS Strix 980ti - 79 FPS
NVidia 1080 (Founders Edition) - 96 FPS
ASUS Strix 1080 - 98 FPS
And this is Tom's review just posted testing Hitman Absolution at 1440p:
NVidia 980ti (reference) - 48 FPS
ASUS Strix 980ti - 53.4 FPS
NVidia 1080 (Founders Edition) - 67.4 FPS
ASUS Strix 1080 - 68.4 FPS
These were just randomly picked. The Founders Edition holds its own with these AIB cards. The differences are almost negligible. This is surprising considering the overclocking headroom from the 1080. Maybe NVidia and the AIB partners expect you to overclock yourself?