We've had them for a couple of weekends now and they are a lot of fun. When I first started researching I figured I'd end up using the hand throttle only like a "mini motorcycle" but in reality, I end up pedaling almost all the time.I'm eager to hear about them
The pedal assist is really amazing - it's sort of like when you first learned to ride a bike and you had your dad or someone else pushing you, that's what it feels like: You start to pedal and then all of a sudden the electric motor kicks to "push" you. The other great thing about the pedal assist is that it "flattens out the hills", that is, you can get to a steep hill that on a regular bike would be a "groaner" and just pedal like you would on flat ground, with the electric motor kicking into assist you, and making it much more pleasant.
The folding bike is on the verge of being too short for me at 6'1" with a 34" inseam, even with the seat post up high. I may invest in a longer seat post. Another possible upgrade is a suspended fork, since the one it comes with is solid.
The only down side is that the "bicycle" components, in particular the gear shift mechanism, is strictly Wal-mart quality. Not terrible but not as good as even my 15 year old GT mountain bike. Of course, these are about the least expensive bikes in their class (by contrast, a Rad Mini would be $500 more) so you get what you pay for I suppose.
Incidentally, I haven't given up on the notion of building my own. I determined for a number of reasons that my old GT is not a good candidate but I'm considering buying a cheap Craigslist find and upgrading it to an E-bike just because I think it would be fun.