Mike FL: Some D610 has the same FATAL FLAW ( dust buildup on the image sensor) as D600 per internet.
The blurry viewfinder is probably due to those folks not adjusting the viewfinder diopter adjustment. You know people .... thats why Apple always ask you to check if your power socket is connected when you tell them your pc couldn't boot up. Also, we see more 'amateurs' using high end cameras that some pros don't even use. Beats me if they could fully comprehend the functionality of the D610.