I bought a pair in October and have used them in the back country twice now. The weight savings vs waist high waders is substantial in my backpack. Also worth noting is that each one can roll up and store inside a wading boot to save pack space.
So far the hippies have performed well, and I haven't babied them. My rear got wet a few times while using them when sliding across rocks (to be stealthy); I am used to that being waterproof in waist highs. The lack of bum coverage will take a bit of time to get used to. I haven't been gentle on them, and so far no leaks.
I haven't been able to figure out how to fold the darn things for the "lower modes" shown in the pictures - I've only used them in the highest position.