I think you guys are being too critical. The specs say that the container holds 3 liters. A gallon is about 3.8 liters, which is the generally agreed upon minimum for one betta, so it's not as far off as some of you are making it out to be. Also, look at the dimensions. It's 35 cm long which is a little over a foot long and 13.5 deep with is just under 6 inches. This seems like adequate swimming space to me. Concerning the fish jumping out and the fact that there is no heater, as long as you keep it in a well heated room and cover the hole with something, it's actually not that bad.
Also, I think the way Dorkhedeos keeps his bettas is fine. From the side view, it might look like the betta is very cramped but from the top view, you can see that it has a decent amount of swimming space.
And for the record, I keep my betta in a 10 gallon, simply because it cost the same as a 5.5 gallon and I figured I might as well get it.