I've had one of these since around Christmas time 2010 and I love the thing -- in fact, when I get around to ordering another binder or two I'll probably just order this again.
I haven't noticed its binding efficiency suffering at all, or certainly not enough to be a concern, and I wear it almost literally all the time. Also, I move around a lot at work (part of what I do is stock in a pet retail store -- i.e. lifting/reaching above my head, bending, lifting 40+lbs consistently) and have had no issues there either.