VERY interesting read. I missed that when it first came out. I guess Shimano has to, at least temporarily, give up across the board compatibility to stay competitive with SRAM and Campy.

I wouldn't be surprised to see the new designs work their way down the Shimano food chain over the next few years until Ultegra and 105 are again compatible with Dura Ace even if they aren't compatible with their current versions.

One aside, the new Dura Ace, SRAM and Campy are still 10-speed despite all of their other changes and redesigns. It seems 10-speed is the limit for derailleur designs, at least within current hub width and chain thickness limitations. If 11-speed or more were possible I'm sure Shimano or SRAM would have introduced it to get an advantage on their competition.