I've yet to come across anyone using them on the hills, but the few I've seen being used on the beach have been fairly quiet. I think there's still a novelty value to them at the moment, but as they become more commonplace, they'll probably become more annoying.
It's clear they do have their uses, though. The video footage they provide is breathtaking - check out Danny Macaskill's 'The Ridge' video as a prime example. And although not mountain-related, they can be invaluable for surveying possible damage, erosion, etc. to tall buildings and structures.
But I think I'll wait to see how abundant they become on the hills before condemning them for such a use. Besides, it would be mean-spirited to berate someone who's using one to video a friend's approach to the summit of their final Munro