I suspected something was wrong with the training effect early on because it was too generous. With cadence I get an occasional outlier in the record. It appears to be related to a sudden change in cadence such as going from walking to running. It doesn't look like it's enough to throw anything else off. Problems with battery life, reboots, and lines across activity screens have not been observed.
Probably some, but not all, of these problems were solved with a factory reset. However, I'm getting a feeling from some of the posts that those who are using external devices are having more than their share of problems. I don't own a chest strap, so I can't test this.
If you are having problems and are using an external device, it's probably a good idea to mention the device even if you don't think it's at fault. It might result in a timelier resolution of the problem. No guarantees as I don't know how things work at Garmin.
The Forerunner series isn't that bad. When the Instinct came out in February it had more bugs than a mattress in a flop house.