Saw Dave last night and had to put my phone in this. Had no issue with it whatsoever, if you do need to use your phone for an emergency it can be removed in seconds. It was awesome being at a show where everyone didn't have their phones recording the entire thing instead of enjoying it. Dave seemed more relaxed because of it too and referred to it before making a few jokes.
I saw Dave at the show in SF where he first tried these cases a few weeks back, and I agree that it wasn't a huge issue and that the show (in a large theater) felt much more intimate and the audience more present as a result. And if the bonus is that Dave's material isn't plastered all over YouTube the next day, all the better.
One of the guys who worked for Yondr said afterwards that most people had been fine with it, but that some of the bags had been returned sliced open with some kind of a knife. Now that's addiction.