I think, and I've been thining about this for some time, that there are basically two groups of retro bikers. Or possibly three.
One group collects bikes and parts purely for the nostalgic value, for the history and maybe even a little kudos in owning a rare part. Bikes are built up for show either using the trickest parts in their immaculate whitewashed garage, or (and this is where the 3rd group comes from) as near as to the original specs as possible.
The other group builds retro bikes to remember the way we used to ride, without all the bells and whistles. The parts may not be as trick, and may even be a bit of a mismatch, but theres a retro spirit in all of them. You could get the same effect buying a £399 rigid inbred but the older parts have more soul about them.
Errm also maybe theres a fourth group that has owned a bike for so long its become retro, then they discover this site and decide to restore it with all the parts they lusted after in there youth.
Oh alright, theres no groups, everyone collects retro for their own reasons. I do it for the purple.