A few years ago, I bought one of these, used but hardly so, for a song. The thought was that it would make a good guest bike, since the seatpost adjusts to any desired height and it folds up to store compactly.
As it turned out, it was used by exactly two guests, one crashed it, and the little Dahon Boardwalk D7 was folded up and retired to the basement.
Three years on, I unearthed it while looking for something else, and thought, hmm, I wonder . . . Took a spin and the first reaction was "what a POS", then I brought it to the garage, trued the wheels, adjusted the brakes and shifter, lubed everything, installed some clipless pedals and a proper saddle, and tried again.
Wow. You know, this little-wheel bike is kind of . . . fun. It is very maneuverable, lively, just unstable enough to keep you alert - kind of like an old 911 with A/X toe-out - the 1x7 gearing is good enough for 20 mph, and the ride is reasonably comfortable.
I think this bike has promise after all. Looking for a used road double crank and front derailleur (with an adapter, a braze-on front derailleur can be fitted) to get more gear-inches. Picked up a used bullhorn handlebar, to get a more stretched out and lower position. I'm going to try commuting with it for a while, to get the bugs out. It'll be fun passing people on my 20" wheel folding bike.
The idea is to eventually have a good-riding road bike that I can take on trips. Bringing a full-size bike is usually too much of a pain.
I've done some research on folders, which now convinces me that the better choices would have been a Brompton (for smaller fold) or a Bike Friday (for more full-size-like ride). But they aren't $150 on CL.