The consensus among photographers out there is that the Nikon D610 is basically a replacement for the D600. The Nikon D600 is an excellent DSLR (which we reviewed here). However, it seems that some users have reported a defective shutter mechanism that would sometimes spew oil and dust onto the image sensor (we did not encounter this problem during the two weeks of testing we had the camera for). Nikon has never come out and officially acknowledged this problem, though they will repair your D600 (should it be defective) as long as it is still under warranty. Consider the D610 as their way of saying, We fixed the problem. If you own a D600, or are planning to purchase one on sale, you may want to think hard about getting the D610 instead.