That's my whole point: 15 miles is normal on a bike; anyone, not just "enthusiasts," can do it, no matter what kind of bike they have or what shape they're in. I'm not particularly athletic, and I rode all over northern Italy for three weeks on an upright 5 speed, doing 60-100 km days without even sweating much (the trick is to take your time, and make frequent wine-tasting stops). I've even seen very overweight people do 15-20 miles on a bike with no ill effects whatsoever.

And for the record, I like Dutch bikes. I'm not sure that Americans will embrace them all that much, due to high cost and limited performance, especially in hilly areas, but they are beautiful and a very comfy ride. (Along with some others, I wasn't too crazy about the clothes, though. I would think a pair of Eddie Bauer khakis and a button down shirt would probably be adequate for a 10-12 mph ride.)