It was purchased about a week ago. Very nice, fits well on the hand. It is not a smartwatch, it is a smart band with a large screen and a couple of extra functions. (smartwatches are mobile phones) It synchronized easily (set the language to Greek on your phone to see notifications in Greek and then change it). The measurements I saw are good, the GPS is very good for outdoor running, it found the route quite well even in apartment buildings, and on a 9.5 km route it showed 9.45 km. The altimeter messed up a bit, but I'm not very interested in it (it showed a significant increase in altitude while the route was flat). The battery is good, with always-on display, continuous notifications, automatic brightness, and 4 exercises with GPS (about 1.30 hours), it went from 90% to 10% in 6 days. If I turn off the always-on display and don't use GPS, I think it will last 10-12 days (the always-on display consumes a lot of battery). The notifications come normally without any problems, the GPS locks in 20 seconds, and it accurately measures sleep. Now, if you have a large hand, it won't look very good on you, but everyone knows about themselves. I have a large hand and it looks relatively small. For €85, I think it's a very good purchase. It's a more beautiful Amazfit BIP S.
(In comparison to my friend's Garmin watch worth €300, the routes and measurements were very close, specifically, it showed the same heart rate and the distance was closer than on the Garmin)
Update (26/11): With daily exercise of 1 hour, the watch lasts for 3 to 4 days (from 99% to 10%). I noticed that it has an issue with battery measurement. Sometimes it drops dramatically fast, and other times it stays at a certain percentage for many hours. For example, I didn't wear it for an hour and it dropped by 4%, while during 5 hours of normal use, it only dropped by 1%. In the sports activities I tried, the GPS continues to work well, it locks even faster now. The notifications come normally, except sometimes they come in duplicates, but it doesn't bother me. The heart rate measurements occasionally go way off. I have woken up and seen 210 heartbeats at some point during my sleep, and during the day they momentarily drop to 50. But these are, let's say, small exceptions. Overall, it is quite good and accurate, I must say.
Update 2 (30/11/20): I saw some reports from others about very bad GPS and overall measurements. Its GPS is quite good for getting the job done. Obviously, it's not of the same quality as those that cost five times the price, but it is good enough and satisfactory. In routes through apartment buildings, yes, sometimes it goes through rooftops, and I find it logical. Even Garmin doesn't have the immense accuracy despite being four times the price. I check the accuracy of the measurements every day. From steps with other devices, heart rate measurements, and comparison with accurately measured routes to see the discrepancy. For €100, the watch is very satisfactory in terms of what it provides. In a 450-meter track, doing 10 laps of running (jogging and sprinting), it measured 4.47 km.
Update 3 (10/1/21): The watch continues to work fine even in a swimming pool, which I tried several times, and even in the shower (with cold water, warm water might cause issues). So, everything is good.