Much like electric cars, they will have their place but until battery power is vastly increased its a fairly small niche were they are actually a useful tool.
I'm am electric car driver and big fan. But I really don't think I'll b able to replace my ocean boat with an electric anytime soon. Mostly due to weight. Batteries are significantly heavier than gas. So until the size and weight come down, I think this will only be a solution for only the shortest of ranges.