Unfortunately, I am among the users that is experiencing a lot of difficulty with the Lollipop upgrade. Despite using the stock recovery, I was unable to update via OTA, so I had to connect my device via HTC Sync to upgrade. The upgrade process went fine and I wiped my cache after to make sure there were no issues.
I ignored the shoddy battery life for the first few days, but unfortunately it has persisted for the last week and a half, so I can only blame Lollipop for it now. Before I could get around 18 hours on a full charge, but now I can only get 12 hours if I am lucky. I have tried various battery-saving techniques, but it has changed nothing. "Android OS" seems to drain MUCH more power than it did under Kitkat.
In addition, I receive a popup EVERY SINGLE DAY about upgrading to Lollipop, despite the fact that I have already upgraded. The only options are to postpone the update for a day or I can install a root app that will disable OTA updates entirely, which is not exactly preferable. Apps in general run noticeably slower under Lollipop - I thought this was only going to last for a few days at most, but it is still prevalent and apps force close constantly. I can't stand having a phone that doesn't work any better (or have any better battery life) than my 4-year-old Xperia Play.
Needless to say, I will be flashing back to Kitkat ASAP. They obviously didn't finish/optimize this upgrade before they pushed it out. :'(
EDIT: I almost forgot: my phone is also overheating when charging (I wake up and get a warning message that the phone is overheating - yes, "never sleep while charging" is disabled), and it uses an obscene amount of data! "Android Operating System" has consumed over 900mb of data since upgrading to Lollipop and I can only use 1.6gb per month, so unless I switch back to KitKat I will also be going well over my data allotment for the month as well. =/