After several days of using Watch OS 4 since it was released as a GM - I realised that the battery life is even better, at least by 4-5% each day. I am using Apples Watch Series 2 Sports. How I am using the watch: - Wake up put it on around 6:45 am. - Use it for messages replies or Notifications check. - Raise to Wake enabled. - Brightness at medium. - Put it to charge back around 9:00 p.m WatchOS 3.X - at the end of the day I had about 72-75% battery. WatchOS 4 - at the end of the day I have around 79-81% battery remaining Note that I use SiRI watch face. I wonder what is your experience with it?