A previous bike of mine (DA-7800, bought in 2007) had it, and I liked both the gear indicator and the ability to control it using the buttons on the insides of the shifters. I used it even with a Garmin, forget the Edge model I had. Maybe it was the Edge 510, or the Edge 305 (?). The Flight Deck was used for speed indication, and while the Edge recorded speed not needing speed on its small screen freed up a significant amount of precious display real estate. It was also somewhat flaky in that I often had to wiggle it to restore contact. On the whole for the times it was great IMO, but I'd take Di2 and a contemporary Garmin or Wahoo unit any day of the week.