I'm not worried about the strength at all. Feels plenty strong to just sit there. What else does it do? I think the things you'd worry about with 7 denier is the same you'd worry about with 1.1. Example, snagging on a branch, both are plenty possible to tear. I think the key is to use it in the same manner you would with 1.1, very gently, and there's no possibility of problems.
As for down proof, I have no clue. I haven't noticed any issues at all in the last few weeks and I'm sure Adam wouldn't put out a faulty fabric in his quilts. Who knows. This is all kind of experiment for all of us who are using them so only time will tell, but I have faith.