Much better battery life than expected. 72 hours in power reserve mode. And 48 hours for just timekeeping. 7 hours for workout/heartrate sensor. All better than the rumors suggested. 1.5 hours to charge to 80% is great, and if you can get through the day with power left it might not even take that long so you could charge it before you go to bed and wear it to bed if you want to do sleep tracking. Even if Apple isn't offering sleep tracking you know a 3rd party will.