If you're interested in the past, then building a 'real' vintage bike is worth the effort. Yes, Delrin decays over time, but as long as it works, it's actually pretty good. And there's no walking home either. I've had my Simplex FD fail on me on my Peugeot PR10 during a ride, and all that happened was that I couldn't shift to the big ring anymore. Not really a big deal when your inner is a 42. If I really wanted I could have put the chain on the big ring by hand.

As a matter of fact, mrs non-fixie and I are about to leave for a couple of vintage rides (the Belgian Retroronde van Vlaanderen this weekend and Eroica Britannia the next) and a week of bicycle touring in France with two bikes equipped with Huret Allvit, which is a 1950's design. Even though we've got plenty of room in the car, we don't even bother to take along extra bikes for the week of touring in between, as we're both very pleased with how this old stuff works. There is a reason it was used on racing bikes and high end touring bikes BITD.