Despite the general views that small wheels are slow, harsh and prone to get stuck in pot-holes, IMHO these views are wrong or at least poorly understood. Small wheels offer significant advantages and almost no disadvantages.
I agree the many advantages of a good folding bike far outweigh any disadvantages, in fact I have yet to come across any disadvantage. I put 3400 miles on my Dahon D7 and have not intention of every buying a road bike. This bike is plenty fast, easily capable of 25+ mph . So sacrificing all the flexibility of the folder for the 2-3 mph faster speed of a road bike ain't worth it!