I've used the Edge extended display with my FR 965 in the past and it has worked great. I did a triathlon yesterday, and while setting up my watch, I selected the Triathlon 'auto sport change' feature on a whim. I then enabled the extended display on my Edge 530. The computer found the watch and went into waiting mode as it should. I did my swim and transitioned into T1 without touching any buttons and based on the data I saw later the auto sport feature worked well. Walking with the bike out of transition I saw that the watch and Edge computer connected. But once I began riding, I heard a beep on the watch initiating the ride portion of the triathlon followed by the Edge losing its connection to the watch. For the whole ride, the Edge kept looking for the watch, to no avail. Luckily, the FR 965 did what it was supposed to do and captured all the info (I do not take my hands off the handlebars while riding on the tri bars, so not able to see any of that data). But it would have been nice to been able to get an idea of distance, time, and effort on the bike computer instead of a 'looking for watch, make sure it is turned on' message on it...
I realize this is incredible hard technology to make it look simple and functional, so when it doesn't work, and I rely on it, it is pretty distracting...especially in the middle of a race.