5d iii lens correction
That's interesting Muresan.
I don't use DPP (should I be?) like those of you who replied. I can't see it making any noticeable difference in how the jpg version of the raw file looks in the camera lcd, so I guess I'll just not do lens correction in camera and do it in ACR (photoshop).
Use it if you want better jpgs out of the camera. You can easily test this if you want, you can enable or disable the jpg correction in the camera's menu menu. Quite good on chromatic aberration in some cases.