Got my D600 back from Nikon a few days ago, with a note telling me it isn't dust-proof! Water-resistant, yes, but not dust-proof?! Guarding their backs, I guess ...
I love it anyway! I'm sure it will have some more dust problems in the future, who cares?! A fantastic camera for me, a poor enthusiast, who sold my beloved Pentax gear to buy this lovely baby! Today I have a nice setup for it: the 28/1.8, the 50/1.4G and the 85/1.8G, plus the Sigma 70 macro, and two classics: 400/5.6 and 80-200/4. If I need a 35 I'll use the DX lens, works quite well (needs some cropping, but not that much)! And I have the AF-S VR 70-300, too, but is more or less is glued to the V1. So no zooms on my D600 (sold the 18-70 & 55-200 today), except that supersharp old 80-200 manual lens!
This oil/dust issue isn't nearly as bad as that happened to a lot of K-5 owners, including me (mine was minor, didn't need to send it off)!
Just tried the 28/1.8G I bought today on it - smooth!