Great question and loving the input!
Garmin 620 here. Haven't had trouble with it, thankfully. The running metrics are not particularly enlightening, but totally cool and I check them occasionally. I use the HR strap, and have been pleasantly surprised that it hasn't been that uncomfortable or chaffed so far. I'm very interested in the 735XT, especially as I'm thinking about triathlons after Dopey next year.
But, I am a slave to the thing.
@DopeyBadger mentioned in his Wisconsin Marathon recap that he 'removed the blind' in mile 25. I'd like to get better at relying on feel, instead of the device, but still want to keep track of my data. Anybody else try this, and does it work for you? (And how do you do it, exactly? Thanks!