My honest review is that I am disappointed. I had the battery on my Apple Watch SE (1st gen) replaced, and the battery life is not as improved as I was hoping it would be. The battery is dead after about 13 hours of moderate use, while Apple says a brand new battery should get close to 18 hours of use out of a full charge. There are other odd things I noticed: it took a REALLY long time to charge the battery the first time I plugged the watch in (something like 7 hours instead of the usual 2?) and sometimes the battery goes from 100% to 94 or 95% after only a few minutes of use? I don't know why this is - it could be that the quality of the replacement battery is not up to par (I understand that Apple makes it hard to acquire replacement parts for many of their devices). It could be that a WatchOS change is causing the battery to drain faster than before. In any case, I was without my watch for over 3 weeks and spent $80 on the repair and I am not sure if it was worth it.