You might think that there is a equivalency between those who think it is a non-issue and those who are returning cameras for fear of cleaning, as a cancellation of opposing views but consider the differences in experience and camera knowledge. I have yet to see a report by anyone who had a good grasp on field to return a camera or be overly concerned. Who would you prefer to believe?
I am just surprised so many new users are shooting at f/22-32 so much that this is even seen. If more people did they would find that all AA filters, mirrors etc have some dust on them, regardless of brand or model.
I think it is a false equivalency. We have very little evidence that oil is involved, but there are reports of dust, which are fading away like happens with every new camera that gets the internet rumor treatment. After a while the complaints just stop, based mostly on how much experience a new user accumulates and how many forums they read. The D7000 for example was raked over the coals by the internet rumor mill but as people got some experience with it, it is being viewed as a great camera with very good reliability. Even the D90, one of the most sorted out digital cameras ever, had lots of initial complaints that faded to be replaced by almost universal praise. We are seeing the same pattern here. That is one reason why experienced users, experts, like Eric above think it is much ado about nothing, any thinking person would give that more weight than anonymous internet rumors. If someone is not really convinced they need one particular camera, there are lots of choices, this one is not for you if there is so much doubt. For image quality there is the D3x and D800 but not much else in the world is better. For speed of frames a used D3s would be a better choice. For lack of needing general maintenance...there are point and shoot cameras which are getting pretty darn good. A decision to get jump into a new system and all the overhead involved(expensive lenses, learning curve, general user maintenance) should be a happy and confident one. In this case you are not so firm in the decision so you should not even consider it. It is apparently not for you.
Regarding the voiding warranty of a camera by doing routine cleaning would be a new one, do you have specific knowledge of this? It would be a 50 year reversal in policy for Nikon so can you provide specifics? Stan St Petersburg Russia