The best part, in my opinion, of the classic bike is the ride quality of the frame, not the quality of shifting.
When I rescued my SOMEC from the ignominy of living out its days as a beater fixed-gear, I was originally going to put it back to its original 7-speed Super Record condition.
After riding my father's bike, which is 7-speed Super Record, and comparing it to my own 10-speed STI shifting, I decided on modern stuff.
Enter Campy Chorus 10-speed. Carbon Cranks, lightweight bars, SLR saddle etc etc.
At that, even with the steel fork, it weighed only 17.8lbs and it performs as good as, if not better, than any hyper-modern carbon bike or even any 2008 steel bike. (I prefer the ride of Columbus EL to my friend's Columbus Spirit-framed Pegoretti Duende.)
As nice as the old, classic bikes look, they can't perform like they're supposed to without good components to support them. The lighter wheels, the stiffer cranks, the stronger brakes, they all serve to highlight how well-engineered and made the frame actually is and it brings with it a whole new appreciation of the framebuilder and his product.