The Camera Store in Calgary has posted a video comparing the D600 and he D610 here: http://youtu.be/CtbgyJgiF0M
From what they say the differences are as minimal as the specs would indicate. Yes, they do mention the dust issue some are having. According to them they have sold hundreds of D600s and they haven't had a single one with the dust/oil problem. So take it as you will. We still don't have official word on how many cameras were affected but it sounds like it's not as many as some people claim.