There are a number of factors to consider when buying a camera (or lens for that matter) and it is the answers to all the points that ultimately decides. Each person will have different considerations, even if their subject matter overlaps.
1. What do I like to shoot?
a) Do I need a fast frame rate?
b) Do I need fast or accurate AF?
c) Is DR more important than anything else?
d) Do I need to shoot in low light at high ISO?
e) Can I control the lighting?
2. How large do I want to print?
3. What range of lenses will I need?
4. Is the exta cost (i.e. camera or other accessories, including computer hardware) worth it?
a) Will it give me improved image quality?
b) Will it give me a competitive edge?
5. Will something that is cheaper do just as good a job?
I shoot a combination of wildlife and landscapes mostly, often in low light. For me, the most important features were good AF speed and reliability, good image quality and good high ISO capabilities. The silent shutter has come in very useful already and dynamic range would be nice, but not a high consideration and certainly not at the expense of something else. In fact the IQ is improved so much over the 7D (despite the lack of reach) and the AF is such a big improvement over the 5D MkII and even the 7D, that the 7D has been relegated to a back up body, instead of the main wildlife body. For lansdscapes, I use filters, which mostly give much better results than an extra stop or two of DR for my style and I can print up to A1 without any problems (at east in theory, I can't actually print that large), so the extra resolution would be overkill. In fact, there are very few lenses that will get the best out of the D800 sensor, even the 14-24 seemed to struggle going by Nikon's sample images, athough sample images aren't always the best examples of what a camera or lens is capable of. You are probably looking at recent, expensive pro-grade lenses to have a hope of getting the best out of the sensor and even then, if you aren't printing very large or pixel peeping, I doubt you'll notice the difference.
