Nothing actually, never even had an issue with the spots. However, I don't like how nikon handled the debacle and I don't like the stories I've read about their cs and warranty issues.
That aside, canons ergos sold me. I made the mistake of holding a 6d at a local best buy one evening and I was sold. Also, call me crazy but I find canons iq more pleasing. I know I'll miss the dr and a few other things from the nikon system but I look forward to canons system and glass.
I guess my biggest concern as of right now is the 6d's af system. Though I'm certain it can handle my son's sports activities being he's only 5 lol.
I'd still like to hear from those who switched.