Yeah. I think after either the last update, or the one before, my 5S battery life has sucked.
I used to be able to work a 12-hour shift with it in airplane mode and only lose about seven percent while listening to podcasts and audiobooks nonstop.
Now, I lose about fifty percent.
Curious. I have a 5c iPhone and an iPad 2 and neither has suffered more than about 10% change of battery life under iOS 8. Your unhappy experiences may be related to other additional causes than strictly the version upgrade.