Another leap forward in camera technology. The improvement in image quality (compared with the D300) leaps out at you most of the time. But in order to get the best out of the camera (maximum detail) I find myself being much more rigourous than with my other cameras.
Great flexibility in terms of correcting errors done during shooting: if you get the framing wrong you can crop, if the get the exposure or lighting wrong then you can go a very long way to get if right in post-processing (if shooting RAW); Lots of useful options
Image sharpness becomes an obsession; There is so much detail that when you look at the image at 100% (as you tend to do when processing in Lightroom) every error in focus area choice or depth of field is immediately obvious.