I've given up my 700c bikes for Bike Friday 20" and now 16" bikes. I lose nothing in terms of rideability as they ride almost exactly like a full size road bike (the only folder with multiple frame sizes
AFAIK). What I love is (1) the lower center of gravity - if you start to fall just put your feet down it it stops falling; (2) the nimble steering especially in city traffic, (3) the ease in carrying up stairs for a short person - I always smacked the wheels on my full size bike, (4) the convenience of popping in the car, on the bus, on the train, (5) the faster acceleration on small wheels from a stop, and (6) not needing to carry a lock with my Bike Friday pakit. Also, the 19 lb weight of my pakit is something I can deal with as a senior female. Hefting a full sized bike around when you're under 5'5" and it's heavy (to me) is not much fun. When I ride with my 30 year old son, he's way ahead of me by the end of the block, but I'm faster out of the gate, haha. Those tiny wheels really take off quickly. Smaller bikes are just less hassle, and they make you smile, too. For those who like a cushy ride, you can get a thudbuster seat suspension add on or use fat tires. I'm fine with a titanium seat mast, it soaks up the bumps just fine, but I also come from years of mountain biking where I learned to lift off the saddle and I do that without thinking about it. I like a good road "feel" even at 68. But then I also drive a stick shift car.