On a charge, 15 miles but depends on your weight and the terrain. My son put 22 miles on one once on a single charge.

Safety wise, yeah wrecks on onewheels can be bad. If you are a speed demon you will break something. If you are careful you should be fine. A set of fangs on the board and a pair of wrist guards are highly recommended. And a helmet at all times.

The safety is what put me off of those. Read a few too many stories about permanent, serious injuries to young people using them (relatively) safely. It does look like a ton of fun though.

Super fun, but it will dump you at some point. I sold mine and bought a better esk8, but will buy again if they ever release a new, improved model.