I've used Forerunner 55 for a week now and here's the list of issues/bugs I've encountered:
• If you stop and resume a workout, the timelines in Garmin Connect cut the part the activity was stopped and display it as continuous. This means the timeline doesn't match with other graphs (heart rate, for example):
The middle part (where heart rate is lower) is when the activity was stopped. You can clearly see when the workout actually ended from the heart rate graph.
• Battery drained from 60% to 15% in one night. Phone connection was off, no activity was running. There was no sleep data the next day (Garmin Connect said sleep was 'unmeasurable') and body battery and stress level indicators disappeared.
• It's been 2 days since and the body battery and stress level indicators are still gone (displayed as "---") although I've been wearing the watch all the time and it did manage to record sleep last night:
• The sleep tracking is hopeless. The graphs show I was in deep sleep while I was lying in bed, moving my arms, actively USING the watch and the mobile app etc. They show light sleep when I actually got up from bed and moved around the house for a few minutes. How it fails to detect that, I don't know. The sleep stages seem to be totally random.
• Step counter seems to track pretty much every arm movement (including teeth brushing).
• There's probably a good reason for that but I find it unusual – and hard to get used to – that the back button is located on the right side and the up/down buttons on the left side of the watch. Most devices/user interfaces have it the other way around.
• There's a glitch in the controls menu (the one you open with a long press of the light button) – if you activate something, the text in the middle does not change – for example: "Phone: Off" still displays "Phone: Off" after I've turned it on. I have to move up and down again in the menu for the text to update:
• Every time I make a Bluetooth connection, I get the 'Access Required: Android stopped the advanced music service..." notification both on the phone and the watch.
...and these are just the ones off the top of my head.
I appreciate what this product TRIES to do but everything other than the usual features (timer, GPS, heart rate) seems to be experimental and should be marketed as such.