I have the Blue 44mm, used 6 series. I couldn’t justify spending $450+ for a new 7 but would do it because I needed a good fitness tracker….hence, decided to give a $250 used 6 a try. The description pegged the watch as ‘like new’ at arms length and promises it worked like new. 100% accurate. The box was well packaged, came w a separate charging cable and silicon strap. The strap could b OEM.Battery life - Better than anticipated. Apple promises 24hrs, I’m seeing more than 36hrs.Resolution - V good. Sharp & clear. Better than a lot of friends watches.Touch sensitivity- Excellent. Accurate (even on the smallest of icons/text). V responsive and no lag no matter how quick or lightly u touch it.Brightness - V good. I haven’t had it fade-out in the Florida sun and can always read it.Fitness tracker - Excellent. The native work out app has multiple modes (gym, tennis, rowing, cycling) and can detect what activity ur doing. It displays pulse, active calories and total calories.Health tracker - Excellent. The watch comes w blood oxygen monitoring, heart rate monitoring and more. I’ve only used the HR & BO and have found the pair to be accurate. Additionally, the latter have helped me fine tune some eating habits as I wasn’t aware how much certain foods affected my HR & BO.Sleep monitor - V Good. I’ve found this has helped me drive towards a better nights sleep.Apps - Excellent. Apple Watch has more apps than u can shake a stick at, and they work well.Apple Pay - Excellent. The convenience of using ur watch over fumbling for a wallet or phone is off the charts. Additionally, it works perfectly.Telephone calls - Excellent. Receiving and making calls is a breeze and has worked flawlessly. I never expected to use this feature but the watch speaker is loud/clear and the person at the other can’t tell I’m calling from an external device. This is especially impressive since the call is relayed through my iPhone.Texting - Excellent. The Siri/dictation features are excellent. I can send receive texts flawlessly (no more phone fumbling) and the manual input works flawlessly too. The only drawback is u can’t select emojis but if u say “happy face”, Siri will insert the latter in character form.Setup - It’s pretty much a breeze. Charge the watch, download the Apple watch app to ur phone. Put the watch by the phone and follow the instructions. Any apps that can b transferred from ur phone will be transferred.Usefulness - Off the charts. This is not so much a watch but a miniature digital Swiss Army knife. The watch is unobtrusive and having so many of our daily digital-needs on a wrist makes life a lot easier.There r a lot more features to suit how u would use it.I thought I would find the short battery life a nuisance, not at all. Plus I don’t use the watch everyday….at times my wrist will go commando or I’ll wear a real watch to mix it up. I would recommend purchasing a protective case for it….the one I have is a chrome silicon thingy that protects against scratches, dings and has a raised lip to protect the screen.I am so glad I gave this ‘6’ a try before purchasing a 7. The leap between the two is marginal (despite what the marketing dept would have u believe). V happy w purchase and hope to keep the device for a long time.