We have had our halfbike for nearly 3 month by now. All family loves it. We used it every day for short distances. The learning curve was actually much shorter than what we expected, as we have been able to ride it comfortably in less than an hour. And it is very much fun.
Ah one caveat: It is shaky as we go downhill and I wonder if it is due to us or to the concept o the bike itself. It will be great if you could develop a standing bicycle for bumpy or faster downhill rides.