I've been thinking about this thread a lot, though I'm not sure I have any new insights. I own lots of bikes, and they all feel different, though I believe I have the fit adjustments of most of them dialed in well enough to work well for me.

But I went to Philly this weekend, and my friend loaned me one of his bikes for two 17-mile rides. (We rode from a suburb into the city for the Philly Bike Expo and then back in the evening.) I had trouble discerning what was unique to the design of the bike and separate it from the fit. The fit was very unusual, with the handlebars a lot higher than I'm used to. It took a long time to feel comfortable on it because of the fit, not because of the bike's design.

Then after we got back, he had me try two more of his bikes. One of them also had the handlebars high, but for some reason, it felt terrific. The other one had the handlebars much too low, and not surprisingly, the bike felt awful, but the awfulness was clearly from fit and not the bike.