I have two sets of the clipless, and two other sets of EZ pedals (one set came with my MU SL - that I have now attached plastic toe clips to, another is a plain set of platforms for toodling around on my Brompton.)
They work pretty much as advertised. The only downside is you have to keep the pedal some where when you take it off. For the clipless, you can often stick it in your seat bag. For the others... kind of a hassle vs. a folding platform.
I think the ideal folding bike pedal would be a folding pedal with SPD on one side, and platform on the other, assuming you could engineer a locking mechanism, etc. Nothing seems to exist like that yet. Someone get on it!