By and large, the Fenix3 has been pretty bug-free for me. I have seen a handful of little quirks, most of which have already been addressed since I’ve noted (and reported) them. I haven’t seen anything that’s systematic, nor anything that was a show-stopper. Finally, I haven’t seen any single oddity more than once (meaning, a repeating issue).
The minor quirks I have seen on production versions of the Fenix3 include some oddities with Live Tracking here and there, such as sessions that showed odd sensor data to people following me live (but my data recorded/shown to me was perfectly fine). Also, a discrepancy where Garmin Connect told me a course was ~14.9 miles, yet when I actually ran it, it was ~14.6 miles – nearly a third of a mile off. It’s not clear to me if that’s a Fenix3 issue or a Garmin Connect course creator issue. Similarly, I did see an issue where the Fenix3 wasn’t reading the estimated paces within a course file from Garmin Connect. But again, it could be that Garmin Connect wasn’t sending them correctly.
Finally, I’ve seen one issue with reboots related to changing power meter data fields during configuration. Garmin has confirmed/reproduced that as being fixed in the next firmware update.
I haven’t seen any GPS accuracy issues, nor have I seen any reboots beyond what I just noted. I’ve not seen any data loss either across not just production units but any pre-production units.
Which of course this doesn’t mean you’ll see something I don’t. I can only test what I think to test, or stumble into during day to day use across swim/bike/run/hike/etc… In looking at other sources, such as the Garmin Forums, I don’t really see any sort of widespread issues either with people that have had the unit going on a month now.