My advice would be not to buy one unless you don't care too much about money, even though they're probably lovely bikes.
The reason I say that is because at some point in the future, you'll have a problem, like no function and a code on the display, or a worn out battery. The only person that would be able to help you would be someone with the Go-Swiss Drive diagnostic equipment. At the moment, they're few and far between and, even then, they might not want to help you if you didn't buy the bike from them.
I would therefore recommend that you stick to well known and common electric systems , like Bosch, Yamaha and standard Chinese systems. The Chinese systems are easy and cheap to fix if something goes wrong so, unless you're DIY incompetent, you can fix them yourself.