I just bought the Halfbike 3 and it's my first experience with the Halfbike. I must say the first month was actually tough and challenging. Learning and riding it required a lot of energy! I also conclude that the Halfbike is only for flat surfaces (hence, -1 star. Sorry, this is just subjective for me!). Had a lot of falls or close-crashes when maneuvering on uneven inclined surfaces (my neighborhood has a lot of hilly areas). I learned it the hard way. Also, riding downhill was very scary at first, especially if your whole body is tense (I was wiggling dangerously a lot!); I eventually learned to loosen up and downhills are not that scary anymore. Haha
Anyway, on the second month, I learned to ride it more 'relaxed' and, lo and behold, it really is fun! It's a really great conversation starter and it's fun to watch friends become mesmerized as they try it for the first time. I can attest that riding the Halfbike becomes fun and great the more time and experience you have with it!