I am sure this has been discussed to great length... but here is why I use "old" stuff on my main randonneuring and long-distance racing bike. Old stuff in this case is Simplex derailleurs with downtube retrofriction shift levers, Mafac Competition brakes, 7- or 6-speed freewheel with triple front, and Maxi-Car rear hub:
1. Downtube shifters are more reliable. I have seen so many bikes that stopped shifting due to lack of maintenance, humidity changes (from the wet western part of the state to the dry eastern part), and other problems. Usually in the middle of a ride or even race. I know good maintenance can avoid this, but I don't even have enough time to train.
2. Downtube shifters make me move my hands more. Less numb hands.
3. Mafac brakes are pretty much the only ones that work with alloy fenders and reasonably wide tires (27 mm true width). Alloy fenders are lighter and rattle less than plastic. They give better coverage, too.
4. Maxi-Car hubs are the only ones that allow me to replace all spokes on the road. After having broken two spokes once early into a race and having ridden 210 miles on a wobbly wheel, I don't want to do it again! (I was very sore from the thump-thump-thump.)
5. If you count the Brooks saddle among "old" stuff: It's the only one that is comfortable for 10+ hours.
6. Old-style handlebars give more hand positions. They have a longer reach (at least the ones I use) for an additional position behind the drops, as well as several positions in the drops, because the drops go further back.
7. The "old" Campy NR seatpost gives me more setback and never goes out of adjustment.
8. To my eye, the old stuff looks nice, and I like using it. You may laugh, but if you don't love your bike, it is very hard to spend 10+ hours on it.
9. Cost: I whince at $ 90 for a derailleur, but compared to new stuff, this is cheap.
That said, I am not turning down useful new technology: I use a Schmidt generator hub and Look mtb clipless pedals. Of course, your preferences may vary. I am not disputing that there is a place for the new stuff. Just not on my bikes!
So, does the old stuff slow me down? Not at all!
Jan Heine, Seattle (who, until 1999, used to race Cat. 2 on a Campy Super Record-equipped bike)
P.S.: All the components I use on my "main" bikes have been made recently in considerable quantities. So collectors, fear not that I will use up the last of its kind on the dusty roads of Washington.