Also seeing significantly shortened battery life (Series 1). I've got used to getting through the day, assuming no workout mode that uses the HR sensor, and 'typical' notifications with haptic enabled. I did two things last week that have a bearing:
1. Updated from 4.2.2 to 4.2.3
2. A couple of days later I had problems with using the Pillow app (see below), so opted to reset the watch completely, reinstalled/paired as new and setup with identical settings to previous (modular display with exact same complications in same positions. The only different in setup was that I specifically skipped all third party app installs to the watch and ONLY installed a couple I used daily (mainly because I rarely used others and found location them on the app picker to be cumbersome).
The reset was necessary to get around a problem with the Pillow app (sleep tracking) not communicating between the watch and iPhone app, so I couldn't start sleep sessions. I'm used to the watch using ~20% battery overnight, and getting through the following day till about 9pm with ~25% remaining. I usually recharge the watch for an hour or so at this time before going to bed and starting a Pillow sleep session again.
The last few days I've been getting to ~10% power by 7pm.
Given that a reset is often cited as a good way of resolving battery issues, it seems odd if that caused the problem. And so that leaves 4.2.3 as a potential culprit.
The only other thing I can think of is that the Watch had 'learned' certain power saving habits based on usage, and that has been wiped and its now going through the process of relearning and might improve over time. I'd not noticed this sort of battery usage in any previous WatchOS release. The only thing that regularly hammers the battery life is using Workout mode, but I rarely do that these days because I don't find the generated HR data to be particularly useful, at least for general exercise period, which for me is long distance walking which the Watch has never really provided useable battery life for.
