[Amazfit] 5nak3:
I'll have a go answering your question :)

The Amazfit app has improved since last year, you can see data within the app e.g. step count, sleep quality (for what it's worth), heart rate etc... But that data is tied to the app since there is no web portal that you can access say on a PC.

The sync still remains with Strava only, I found that if you install the MiFit app from the Google Play Store you can sync the watch to that which can then export the data to Google Fit. Though I didn't really find the data in Google Fit to be all that great / useful for it to be worth my while having 3 different apps installed.

Another limitation I've found with the watch is that calorie count is not all day calories. It is some very odd "active" calorie count figure. That is to say, if you wear the watch and sit down all day doing nothing you will not see the calorie count figure increase as Fitbits or Garmin devices since Amazfit have not considered BMR in their calorie counting whatsoever.

If you start an activity or you walk all day your calorie count will increase. I guess you could treat the calorie figure as active calories...personally I was annoyed with it at first but realistically I don't count calorie intake, so why would I worry about calorie expenditure? I just use a watch face that doesn't show calories and forget about the usefulness of that metric.

My use case for the watch is primarily fitness based, always on screen and notifications. I'm happy with the always on screen and notifications. Fitness and general health leaves a lot to be desired though. In my experience the things I've noticed include:

* Sleep tracking is not great, it gets the times correct most nights, but I'm pretty much exclusively in light sleep mode. Maybe the watch is too sensitive or I trash around in my sleep, I don't know. I hardly look at this outside of seeing how many hours sleep I got.

* Calorie count not worth the hassle due to the above

* HR tracking is...well, I'm still not sure. Resting HR can have me a 50 bpm one minute, the next I'm at 90+ bpm while sitting at my desk. Other times it can go hours nailing a pretty good representation of HR as I'd expect. During exercise, don't expect weight training to be anywhere near accurate (this is true for most optical HR sensors), running workouts do have drops where I could be at 150 or 160bpm one second then <120bpm the next but the trend seems to be correct most times.

* GPS might not be as accurate as some other running watching, but does exactly what I want. I've not noticed any major drift or drop outs in GPS, just make sure to wait for the GPS lock before starting your activity.

With all that said it might sound like I dont like the watch. But I think even with these issues I'd buy it again. Mainly because it was cheap (compared to rival products), offers most day to day benefits i wanted (notifications, always on display, several days battery life), it also has GPS and exports to the exercise tool I use.

To try and make the fitness aspect a bit more appealing for me what I've started doing is running with a second hand vivofit 3 in my pocket reading HR from a strap and use the Amazfit for GPS. When I get home I've written a script to replace the Amazfit HR with the Garmin HR and upload that to Strava. Works well, allows me to keep Cadence, GPS info and get a more accurate HR reading. I could use this setup for weight training as well, but realistically I'll never be HR zone training during a weight workout so as long as the Amazfit can upload workout time to Strava I don't care about that data.