I notice I'm getting much less usage time per hour, as well (I have an iPhone 6). For example, before 8.1, it would take about 3 hours of usage time to get to 70%. Now it only takes 2 and it gets worse after that. Attached are screenshots I took of the battery usage before and after the 8.1 update.
The first image is pretty normal usage timings for me (it was taken Monday, October 20th). The second image (from yesterday), is after starting out with 100% in the morning.
As you can see, it's quite a huge difference. The weird thing is that messaging seems to take up more battery life than it used to. Yes, I do text quite a bit during the day but the frequency of this has not changed between now and October 20th. It shouldn't be using THAT much battery life. I took it to the Genius Bar day before yesterday to ask them about this problem and the girl told me that she saw some crashing from the Messages app in Diagnostics Information and she felt that maybe since the update, there was something causing that app to use more battery. So she suggested erasing the phone and restoring from an iCloud backup. I did this the same day when I got home but, as you can see, the problem is no better (though there are no more crashes listed in the diagnostics information).
I have no idea what else I can do to fix this and I'm getting really tired of having to charge this twice a day now (I used to have to do this with my iPhone 5, as well). If anyone has had a similar problem, I would appreciate suggestions. And before you ask, I'm doing all of the normal battery saving tricks, like turning off background app refresh, not having it check for mail all the time (it's manual), brightness is down, I turn wifi off when not using it, I don't leave apps open, etc etc etc.
Any help would be appreciated. Thanks in advance!!!
Pooja