Originally Posted by Dave Mayer

By the mid 80's Shimano had perfected the rear derailleur. The first generation of Shimano 600 indexed derailleurs were as good as it gets, and didn't suffer from the compatability problems of the early Dura-Ace units. I can't see any substantive improvement in derailleur-based shifting since then.

Now to expand the debate....

As far as the best shifting performance, everything I've ever used pales next to my Alfine 8-speed internal hub. I have used pretty much every variety of derailleur-based system going back to the early 70s, right up to current STI and Ergopower systems. But the Alfine shifts correctly every time. There is no hesitation, no mis-shifts, no noise, no in-between gears, no clattering or complaining. The shifting is utterly reliable, quiet and fast. Plus the hub has a silent clutch, and it is quiet while coasting, and it engages the chain the instant you apply power.