For me it is great! We are always hiking outdoors near rivers and streams. I usually have to put my cell in a zip lock bag so it won't get wet. Then it is a pain in the you know what to get out to take a picture.
Yeah, haven't had it on any of my previous devices but am looking forward to it on the Z1 Compact. Living in Florida affords us the opportunity to be around water year round and while it won't help a ton at the beach, we have a pool and also spend a lot of time at Busch Gardens, Disney, Sea World and their water parks so not having to worry about the phone getting wet (or use a plastic bag) will be nice.
And contrary to it being the 'Sunshine state', we have rain and thunderstorms pretty much every afternoon/evening over the summer so again, waterproof is a nice bonus.