I did enjoy riding my old racing bike (1973isn Raleigh Competition, 531 Reynolds, so too old to be a 'road' bike!) in New York last summer even though it was acoustic. It took me a few days to get used to it, but just being on a 23 pound bike was a blast in its own way. I found that I had gotten into very good shape from eBiking here in Los Angeles, and I couldn't believe how puny some of the 'big hills' in Central Park seemed!
Also, for fitness rides on my Trek kit bike, I find that when my goal is to get the best workout possible in the shortest amount of time, I use the motor a lot less, so more of the riding is like an acoustic bike.
BUT -- and this is a big "but" -- both those bikes were handpicked by me and were modded for my riding style. The Trek has seat and stem suspension and a megarange cluster, and the Raleigh has a very low gear in the rear cluster as well. They are both outstanding acoustic bikes in their own right.
Renting a beach cruiser or some other random bike -- particularly a heavier one -- I would probably have the same reaction you guys did. When we visited the Aran Islands, we rented possibly the worst-maintained mountain bikes I have ever had the misfortune to ride... my wife's was terrible, and mine was worse-- I think it had two gears that worked. Of course, we had so much fun exploring, it was such a weird place, that it didn't bother me as much as it would elsewhere.
But when we were done, I did encourage the shop owner to take my bike out behind the barn and shoot it. He was a good sport-- played right into the joke, said something like, "Aye, I knew her time was coming, I'll call the vet." I hope he did!
But yes, I love my bike! In terms of how fast and how far it can go, I've never owned anything on two wheels like the Motobecane. Till death do us part, baby. You will have to pry the bars from my cold, stiff fingers!