Also purchased a GTR Mini prior, and gave my wife a GTS 4 mini. Battery life is outstanding, and so light, I forget I'm wearing it. I'll never go back to Samsung.
Overall, I really like the watch and would buy it again. Battery life is great. I'm not sure the sleep data is very accurate. I can get up and be walking around and sometimes it's still in sleep mode. The bluetooth setup was a bit confusing though it stays connected to my Pixel phone and I like getting the text and call notifications, as well as having the ability to answer or make a call. Being able to answer a text with a canned response is very helpful. Heart rate monitor seems accurate compared to a BP/pulse arm cuff, as does oxygen data. I've only used the biking and walking programs but the information seems accurate. I used it in a pool without any problems. The display and overall appearance of the watch are really nice. Can't beat it for the price.
Had the T-Rex for awhile and it still performs flawlessly even after all the **** I've put it through. But I am now hooked on the GTR 4. what a great piece of work. So many features, the numerous and growing number of watch faces, battery life, GPS accuracy, It's ruggedness is apparent right out of the box. Set up is easy and the display is clear and crisp. I started using the Aura sleep recently and amazingly it has improved my sleep habits. Guess it helps to have a sleep coach on your wrist. My complaints, First I wish the app would auto connect to the watch that I was wearing at the time. i.e.: would automatically connect to my T-Rex or GTR 4 instead of manually needing to do it in the app. It could just be something I'm missing in my settings just to be fair. Secondly, I would like to see a workout selection for "Construction" or "Manual Labor". 8-10 hours of heavy construction work will burn a lot more than a 30 minute minute workout. Probably a tough nut to crack. For a price that can't be beat, its a beast. I'll take it over an Apple or Samsung watch any day. Can't wait to see what's in store next from Amazfit. Keep up the good work, it's impressive..
I have really enjoyed tracking my sleep and exercise. I’m an avid tennis player (4 days a week) and the watch has exceeded my expectations with all of the data available from my workouts.