This Lens sounds great and the DXOMark score is very good.
My question is how useful would this lens be ?
Here is my take on this and I might be completely off here so please feel free to correct me if i am wrong.
Consider the scenarios

A. Landscapes Usually F8 or higher is preferred for large DOF. so F1.8 wont be that useful.
B. For group shots the DOF would be really thin. So a Smaller Aperture would be useful.
C. For portraits it sounds great but there are other primes in that price range. the 18-35 range is not great so even with a prime you can walk forward or backward (most cases) to get the shot.
D. Walk around lens : The range is too small to be carrying this lens only.

I love the idea of owning the lens and I think this might be a great lens for people to start with (ditch the kit lens and get this) but for people who already have a few lenses like 17-55, 70-200mm f/4 L,15-85mm f/3.5-5.6 IS Lens and 10-22 this might not be the ideal lens.