The D700 is more comfortable. It's ergonomically designed. My pinky finger has a place to rest, your shutter finger is perfectly positioned, the front command dial is spot on. It's got heft to it. Still my favorite of all Nikon cameras ever.
The Dƒ is shorter and much lighter. It doesn't have the nice cushiony feel of the rubber and my pinky finger dangles. If it were I smidge taller I wouldn't complain (everyone is in for the ultra-compact these days). The shutter-release button isn't right there, but it's not uncomfortable to find. It's just like an old F (I put one on hold today). The aperture dial is a little awkward, it's smallish and is a stretch to reach in portrait orientation. It's much lighter. I'd say about D90-ish, maybe a little heavier.
It's definitely got that old camera feel to it. It's not a DXXX. Those things are designed for all day pro shooting. While this will be my main camera from now on I'll probably use my D700 over it on 8-10hr sporting events.
I haven't put any pro zooms on it yet, so I can't really tell how it's going to balance out, but the 50mm SE is perfect for it. I'm glad I decided to go kit instead of body only. The Sigma 35mm f/1.4 actually kinda dwarfs it, but it's still a nicely balanced combo.
Now anything that sounds detrimental don't take it that way. This is a camera that isn't built for comfort. Nor is it built for speed. It's stylish and that comes with the price of not being the most comfortable camera. I knew that going in. This is definitely a "thinking photographer's" camera. Any design quirks are pretty obvious going in. But I like the style and I'm sure I'll get used to it and it will feel like "mine" in a short time.
The IQ is stunning. I'm shooting Gary Clark Jr. tonight so this will be my first chance at putting both the Dƒ and my new M9-P through the low-light concert test.