The halfbike is really really fun. It is also really really hard. Much harder than I thought it would be. I got mine late in summer, practiced a few times a week, and put it away during the fall/winter. It's just starting to get nicer here so I took it back out today for about 45 minutes.
I'm at the stage where it feels like this is NEVER going to get easier. Im giving myself credit for effort, I finally am able to go in a straight line on a completely flat surface and can turn left and right if I have enough room. But the amazing maneuverability and comfort of the people in the video feels very far away. But I'll keep trying.