I raced a mid-80's Torpado last year in ten cat 4/5 and 40+ Masters races in USCF district 20. The bike was in 80's trim with GL330 wheels, retro-friction shifters, 7 speed freewheel, etc. Although I typically finished in the top ten (one 2nd place ...wow!), I was convinced by the end of the season that I was perhaps at a slight disadvantage with the older components.
In particular, if you tend to be the sprinter type, index shifting sure makes it easier to get the right gear in an accelerating 30 mph run for the field sprint. I now have a new Record 10 group on my race bike and would not give up the close ratios, hands on the bars shifting, and better braking for the USCF race environment. I feel faster and safer, especially toward the end of the race when ease of shifting one tooth up in a tight group can make the difference of getting dropped or hanging on to the break away. Without index shifting I may not choose to shift if I am in a really tight pack environment and thus not be in the right gear or have the power to react to an acceleration. It is a slight edge but that is what racing is all about.
For Tuesday night training races or fast group rides none of this really comes in to play, at least for me.
Paul Raley Racing 40+ Masters in the "Leonardtown Criterium" the Sunday