I have an iphone 4 16Gb and my gf has a 4s 16Gb, after upgrading from ios 7.1 to ios 7.1.1 I noticed faster battery drain.
I did a search on google and found suspicious articles about better battery life on the latest fw.
Needless to say those articles are all followed by comments of users which tell the exact contrary.
For example zdnet writes: "iOS 7.1.1 brings with it better iPhone battery life"...
while users comments are like this: "Battery life is dramatically worse after iOS 7.1.1 on iPad - I've never had any problem with battery life with any iOS on my iPad. Since updating to 7.1.1 however, I noticed a massive drain on battery life.... almost a 50% drain overnight (from 100% to 55%) while not being used and today while being used, a dramatically fast drain in battery life every few minutes."
So what's going on here?
I was fast enough to revert my iPhone to 7.1 using iTunes and a signed 7.1 IPSW file and guess what?
Battery drain disappeared.
My gf for instance refused to go back and kept iOs 7.1.1 even if she had notice the battery drain issue.
These two phones had their battery changed in the same day with new identical blue-star ones 2 months ago.
Now please take a look at these screenshots, the first is from my iPhone 4 reverted to ios 7.1 while the second is from the iPhone 4s with ios 7.1.1.
Both phones were charged to 100% from zero.
As you can see I got 6% battery life from 100% with a standby time of one day (24 hours) and usage of 6:32 hours.
Now to my gf one:
While she had same 6% more battery life her standby time from 100% to 6% was of only 12:35 hours and usage time of 4:38 hours.
That's make a terrible ios 7.1.1 battery performance, it's only 52% circa of standby time and 70% of the usage time of my iPhone 4, she had more or less my same performance before upgrading to ios 7.1.1.
The use of the phones is similar (whatsapp, browing, messaging and little calling).