meh
If you're a casual cyclist, of course you can get by with a folding bike. I exclusively used folders for about 2 years and I usually ride 150+ miles a week. Nowadays I vastly prefer my $350 steel 700c road bike for the superior ride, lower position and drop bars. I doubt I'd do another century on a folding bike, unless it was top-notch (e.g. a custom Bike Friday).
And
afaik, the Dahon and Montague 26" bikes are, well, not exactly stupendous quality. You'd be much better off with a $400 hardtail.
If you do centuries, fast club rides, MTB or any kind of racing, you are far better off with a regular bike. Otherwise folders are fine.