The D800 is a less forgiving camera but its capable of the peak image quality that is currently available in DSLR full frame format. Yes, I am in St Petersburg Russia where we got our first snow(that stuck) of the season. I've lived here for 9 years after moving from my native California.
Seriously, consider that the D800 is a great camera but it might not be a general purpose camera that the D600, D700 or D7000 is because people have such high expectations of the 800 that when the same techniques are used, the results are similar to the quality that their old camera from which they learned their habits. When breaking those habits, however, and using it with more deliberate consideration of each shot, the results can be spectacular. I would not trade mine for anything(except possibly a D800E). The easiest camera I've ever used to get good images was the D90, very forgiving and a solid competent camera. The D7000 took more serious control input by the user and the D800 has been very gratifying in the results but it is not as casual a device to use. Depending on your uses, the D600 might be the better camera for you. Another consideration is the upgrade most users of the D800 have had to make to their post processing system. The files are big, really big, so a fast computer with fast I/O and calibrated monitor goes a long ways in reducing frustration in the long transfer and processing times.
Cleaning your camera, whatever model, is a easy process that is also safe for the camera. You clean your windows and mirrors without damage yet the glass has a lower hardness rating than the silicon of the AA filter covering the sensor. Just don't scour it with diamond dust and you should be fine. Dirt in most cases is not related to a defect in a camera. There have been a few shutter motors which had defective seals in the D7000 which generated a distinctive splatter pattern, but even those motors with bad seals were quickly taken care of by Nikon under warranty. Stan St Petersburg Russia