I saw someone in The Hague on one of these. It looks like a very good way to kill youself.
Still, urban commuting really lends itself for awesome things we grew up with like skateboards, unicycles, rollerblades and all that. I've been traveling with my skateboard ever since I needed to catch trains to get to work and missed them frequently.
However, I can't imagine many people buying an electric unicycle for $2000 USD. That is very expensive.