I think you are quite right on all points.

My girlfriend has a Dahon Piccolo '04 and it is not bad att all, especially at that price point. It is a bit heavy for its size, but that is not much of an issue when riding or when using it for a train, car or bus commute combination. On the London Underground, she struggled a bit when carrying it up and down all the stairs though. She has joined me for a few day and weekend rides on the English and Swedish countryside and it held up well. No centuries, but up towards 40-50 miles in a day. We've added bar ends, a Carradice Rack Box and a suspension seat post. Schwalbe Big Apple tyres may be an future upgrade when the old one wears out.

I think most of those who put down 16" folders for longer journeys either have no other experience than their own 20" folder and only speculating, or they are comparing with an very old/inferior 16" model which is not fair. On my "dream wish-list" for upgrades for my "Presto Lite Tourer" would be stiffer seatpost and handlebar, more gears and maybe longer wheel base, but not 20" wheels..

/MoeŁ