Nikon make some of the top DSLR cameras in the world, and the Nikon D4 is probably their best model on the market (tied with the D4S), and marks pretty much the best that Nikon have to offer in the world of cameras. This camera is really geared toward the professional market, and has a price tag that will confirm that.
The most common, unavoidable issue with all DSLR cameras, is dust getting on the sensor, which occurs naturally if you change lenses a lot. This customer brought his not working Nikon D4 to our store, as he was getting some spots on pictures, and was worried that he had a damaged Nikon D4. Thankfully, we were able to put his mind at ease, and inform him that the issue was being caused by some dirt, and that sensor cleaning was all that was required. Once we had the dirty Nikon D4 in our work area, one of our engineers completed the Nikon D4 sensor cleaning in a few hours, getting the camera back to work in no time.