It's also very safe to try out and do, which is counterintuitive to most people who haven't tried. Overwhelmingly the most common failure mode on a unicycle is that you just stop riding it, and then it either gets ahead of you or behind you, and you hop onto the ground.
Your body's also always approximately vertical no matter what they incline you're riding up/down is. So e.g. riding down stairs on a unicycle is much safer than on a bike, if you screw it up you just let it roll ahead of you and you're standing on the steps.
I'll do that without hesitation on a unicycle, but on a bicycle there's no way I'm doing that on on anything except a mountain bike I trust.
Ha. My experience with a unicycle was the exact same as my experience with Segway and Hoverboard: flat on my back, knocked-out cold, with back-sprain that lasted months.
But then there are 36 inch unicycles, which can go quite fast. I started with a 24' (< 10 km/h), then I bought a 29' (< 18 km/h). The 29' does feel fast. One day, I'd like to buy a 36', which would be a bit slower than a bicycle, but still quite fast. Some people ride them around the world [42].
(1) In Germany we do this in clubs and proper sports halls as seen in the video with elastic flooring. Don't attempt tarmac until you definitely know what you're doing.