One of the most awesome things on this planet. It is good that you have 14 days to send the bike back, because you might seriously consider it. Resist that though, and give the bike a chance. Or even many, you will not regret it. After four days my biggest achievement with the halfbike was driving around 250 metres in a straight line, without falling. And after a 45-minute session I could barely walk, as the muscles needed to ride the halfbike are rarely used otherwise (unless you live on the top of the Eiffel tower). Anyway, I started to love it. That feeling when the bike is finally riding and I am able to control it is very rewarding and definitely makes up for a really steep learning curve. After a few weeks I am able to quite comfortably drive for around 4 kilometres - and it all comes naturally, without thinking. Despite that, I know that the halfbike is definitely not for everyone. You need a lot of motivation and will to want to learn it (and master it), but at least to me it is definitely worth every second spent with it.
All the best, Miki