I have a 306xxx serial number D600 that has the dust/oil spot problem. I purchased it from Adorama during the Xmas Deal but it was backordered and shipped in early January. I noticed the dust spots after about 2,500 shots at f/11. I was able to blow everything out with a rocket blower, it appeared clean at f/22. Since then I've shot another 1,000+ shots and I just tested today and there are more spots. I blew it out again and was unable to remove all of the spots this time, I am now contemplating a wet clean or sending it to Nikon.