iPhone 5 plain. iOS 7.1.2. Virgin Mobile. Had it about a month.
I noticed that all of the selfies I had taken with Instagram were reversed. This was odd to realize; I have had the phone for a month, and when I see a reversed selfie it looks normal to me ... I part my hair on the left, and I didn't notice that all of my avatars for things had my hair parted on the wrong side. I was reviewing some Facebook photos and it was very obvious that some of my pics have my hair parted on the wrong side. It was kind of weird figuring out that the ones that looked right were the wrong ones...
So I played around a bit. With the built in camera app, when I am framing a selfie, it sure would be awkward to try to center yourself in the picture if the image wasn't reversed. I've had devices with front-facing cameras where you could un-reverse the image, and it is quite disorienting to try to center yourself. So I get WHY the image is reversed (one of the reasons at least). I noticed too that when I snap the selfie with the built-in camera app, that the picture un-mirrors as it takes. There is a brief animation as the image flips side-to-side.
For me and my phone/situation, it is when I use Instagram to take pictures from the front-facing camera. Instagram just seems to grab the actual image from the screen, and not do the un-mirroring that the built in photo app uses. So, my solution is to not use the Instagram app to snap the actual selfie, but to use the built in phone app to take it, then afterwards I open the photo in instagram and do my tweaking. Just slightly less than elegant for now, I am hoping that a future Instagram update will give you control on whether to un-mirror the front-facing camera. But I see this as my phone working correctly, and the app itself being the thing that is buggy. In my case.
-Steve