I've read about the battery drain issue as well, although I haven't experienced it. About 6 months ago my 4s started shutting off when the battery reached 20%. My wife's will run all the way down to 1 or 2% before shutting down. I tried a full restore as well as recalibrating the battery sensor. The restore didn't help and the calibration lasted a couple of days. Now I'm back to shutting off at 20% but I usually don't let my battery go that far down anyway. I figure I'll upgrade to the 5s next spring (or the 6s if it isn't a phablet) so I'm not messed up about it.