I bought this pack in preparation for my first trail race. It is fairly simple to get a snug fit that doesn't bounce. As I run over the course of a few hours, I find myself tightening the straps because I've been emptying the bladder. It is SO EASY to readjust this pack while moving.
On long training runs I generally use a small flask with 3-5 servings of gel, some electrolyte caps, and the full water bladder. I'll put the key for my car into one of the cargo compartments and off I go!
My only concern is that perhaps the thin(ish) straps will bother me on longer runs, but I have only run 2 1/2 hours with it so I'm not sure yet.
I am considering the Adventure pack for longer excursions, great job Orange Mud!