My 1 year warranty is about to expire on my 5D Mark III and thought I should send it in, to get the light leak phenomenon fixed. I've verified my serial # as one that is affected by the phenomenon and opened a case with Canon. They quickly responded and sent me a shipping label. I also had to map out a couple of small dead (white) pixels using the sensor cleaning technique, which worked, but mentioned that as well for them to take a look.
I've only heard good things about Canon service, but for those who have used them, how satisfied are you? I'm really nervous and hope that they do a good job. They have to open the body to insulate the LCD, which means that they need to peel off the grippy texture surface to access the screws. I hope it comes back like new as I've taken good care of it.
Going to feel odd not having a camera in hand to grab and go.