Seems like there are a few bugs I have experience and seen here as well.
1. Vibration alert setting has its own life... EVERY time you sync - Vibration alarm setting is turned off.
2. EPO file reports expired in System/About menu. (EPO files helps GPS get fast lock) maybe only display issue - or maybe it really does not work
3. [Added 19/03] - huge issues with stairs - My 3HR counted more up than down. On the 5X it is the other way. My 3HR was reasonably right and about 1 set of stair climbs out in a day (so about 5-8%) where the 5X shows about 30-40% too few stairs climbed.
4. [Added 19/03] - Compass Crash when adding maps?
5. [Added 19/03] - Basecamp Export track crashes 5X so only full reset brings it back.
Any others?