I am still using S4 SS. I recently did a battery service so I essentially got a brand new watch. I am very happy with the performance and all the features. There is not a single feature on S5 or S6 or S7 that I would need or even want, and I don't believe there is anything compelling about S8 either, so I will continue to keep my S4.
I think S4 is the keeper, just like iPad Air 2 and iPhone 6S used to be for many years and still might be!
I think S4 is the keeper, just like iPad Air 2 and iPhone 6S used to be for many years and still might be!