Anyone know if this bag interferes with vision?
it does if you wear it over your head.
If you're talking over-the-shoulder vision, then yeah it does. 9/10's of all messenger-style backpacks are going to suffer the same fate though. It's not as bad as, say, the Chrome Backbone, but it does create a blind spot.
in defense of the backbone, i have one, and it's not that bad. i just have to "tuck" my head and chin a little differently to see around it. not a huge deal.