I have had the D600 for about two weeks, and have short a couple hundred test shots. While I've seen a few spots of dust when at f22 on blue sky, I really have not seen an unusual amount of dust. I blew it off and it stayed gone. It was not visible at any f stop I'm likely to use a lot, and it was only a few that I had to look hard to find.
I kind of expect a few particles of dust every now and then. Definitely no oil in this case.
Sometimes folks get very excited about a problem that ends up being limited to a small number of bodies. I can't say that is what is going on in this case...maybe I bought late enough to have a "fixed" model, but what I'm seeing at this point is really no reason for concern.