My buddy has one of these: http://onewheel.com/
It's very well constructed and it's his daily transportation to and from work (weather permitting).
The problem units all seem to be inexpensive products built to fail. The same is true with second hand batteries for laptops and has been covered by the media.
http://www.howtogeek.com/172680/danger-why-you-shouldnt-buy-...
The trouble is with Hover Boards you get shoddy quality electronics gear with dangerous power sources. It's a terrible mix.