Pairing between my Android phone and my Garmin Fenix 3 watch is about 85 % reliable. When I look at the Garmin forums for the F3, it looks like some people have great luck with pairing and other people do not. For what it's worth, Bluetooth pairing between my phone and car isn't completely trouble free, either.

Live Tracking works pretty well for me. I use it on almost every ride. The other day my phone fell out of my pocket, it broke open when it hit the ground, the battery went out, and the phone shut off. When I got it back together and on, Live Tracking never resumed. Also if I stop my cycling activity, that stops Tracking; if I resume the activity, Tracking does not resume. Those are the kinds of problems I have, as a software developer you'd call them edge cases. In terms of going for a ride after work and having my girlfriend be able to tell when I'll get home, it works pretty well.