I'm not sure if anyone at Garmin reads these forums (if so great, if not can someone tell me where I should send these issues to?), but I'm having the following issues with my devices and Garmin Connect Mobile for iOS. Just for clarity, I have an Edge 520 and Forerunner 735xt, both paired over bluetooth with the iPhone's Connect Mobile app.
#1: The first issue is why is there no manual sync option for the Edge 520 in Mobile Connect like with the Forerunner 735xt? It seems the only way to toggle a sync is to reboot the device so that it repairs with the iPhone. This seems nonsensical.
#2: If one changes their user profile training zones on any device (Edge 520, Forerunner 735xt, or the iPhone), it doesn't push those changes across all devices. This is quite frustrating. The Edge 520 and Forerunner 735xt both has the option to auto-detect max heart rate. That should automatically be synced across all devices. Similarly, the Forerunner 735xt has an option to auto-detect resting heart rate, so again that needs to be synced across the devices so that my heart rate training zones are properly set, given that I want them based on the %HRR. To have to manually change them continuously is frustrating.
#3: Why can't we initiate software updates from the Mobile Connect app? That would be useful to avoid having to plug the devices needlessly into the laptop.
#4: My Strava segments are syncing properly with the Edge 520 but Forerunner 735xt doesn't always pick up the latest changes. When I add segments they seem to sync up, but those that I've removed (are no longer favorites in Strava) do not disappear from the device.
It seems to me these basic compatibility issues should be resolved.
edit: I'm running all the latest software and firmware. My iPhone is a 5S.