@R8R - The D3 is a great camera. The high frame rate is an incredible tool. I have a D3, D4, D800E. I had a D3S, but I sold it (then ended up buying the D3 when I couldn't get a D4). Thus far my favorite is the D4. The D800 and the D3 are really entirely different cameras. For sports, wildlife, events or reportage, I would prefer the D3 to the D800. For portraiture, architecture, landscapes or studio work I prefer the D800. As a single camera option, the build and autonomy of the D3 can't be beat (although the D800 build is very good as well). From experience I can say that the fps can be very habit forming.
I have several DX cameras, and I have become stuck on FX, I love the viewfinder and the wide FX glass. I have taken a lot of great shots at 12mp. I previously posted this Photo to PAD:
It was taken with my D3 and is on my wall printed at 42 x 28 ... it looks great.
Disclosure: I am going to be selling the D3 as I think I am through the infant mortality phase of the D4. Drop me a line if you want more info.