I received my twin quilt with water resistant down yesterday. It's the 20 degree quilt in long, and I went with 25% overfill rather than 30, thinking that the WR down won't suffer as much loss of loss in humid conditions, the shared body heat will make it slightly warmer than the single, and partly to claw back a little of the increased weight with 800 fp down. Part of the decision to go with WR down was because I live in an area with hot, humid summers and mild damp winters. Mildew and mould are a problem, and I hope the water resistance means I can worry a bit less.
The quilt had been in transit for 4 days, but when I took it out it lofted immediately, even without shaking. Anybody worried that the treatment might affect the down's ability to loft can be reassured. My wife has a ZPacks 20 degree bag with the normal down, and I can't notice any difference.
Obviously, I can't comment on long-term durability, - or even how it copes in the field. I have a couple of trips coming up in the next 3 weeks, so I should be able to say a bit more after that.
I don't like to comment on gear that I haven't even used, but I guess no one has much experience with these quilts yet, either.