Depends what DX bodies you are comparing. I will agree the D700 craps all over the D80. But comparing the the D7000 to the D700, the gap narrows. While I will say I prefer the D700 overall, going back to my D7000 after two weeks of FX-bliss wasn't all that bad. Things I don't like going back to, tiny DX-body grips, what I consider a pitiful AF system, and button-placement. On the D7000 the ISO, QUAL, and WB, buttons are overlaid on top of the back LCD screen buttons and it is a pain in the ass compared to the D700's version where they sit on top of the mode dial, great design! While shooting a fight, I LOVED that the D700's AF system, 90% of the time it was perfect and fast (though not flawless, it still tracked once in a while), and the grip just feels right.
Things I didn't like, I thought my 50 1.4 D was my perfect lens, the bokeh looks nice, its sharp as all hell and nice and compact. Most of that is still true on the D700 but I noticed that after I had uploaded the images onto the computer how ugly the edges were, which was not a problem on my D7000. And I knew this would be an issue, I know the differences between DX and FX but I just didn't internalize it so I was kinda shocked at the colour fringing. Almost makes me want to mount medium format lenses on the D700 just to compensate. Also the focal length was not what I was used to. I was used to the 50 being more like a 75, which was close enough to an 85 to make it a great portrait lens. The 50 on FX, not quite as great. But that's easily remedied with a thousand bucks. I didn't care for the "big bright" viewfinder everyone kept telling me about, I didn't really notice it. And in my opinion the noise performance on the D700 is WAYYY overstated. As far as I can tell it's only about half a stop better than my D7000. ISO 100-800 is virtually indistinguishable, its at 1600 that the D7000 actually really starts to show the effects of noise on image detail and dynamic range. The D700 was noticeably better and at 3200 the gap just continues to widen. However, comparing images shot at 1600 on the D7000 and shots at 3200 on the D700, the cleaner images are still the D7000 at 1600 so I'm guessing 3200 on the D700 is somewhere like... ISO 2400 on the D7000. It's still a noticeable difference, just not the black-magicery I built up in my head. And that for me is the difference between comparing the D80 and the D700. When I had the D80 I was constantly frustrated with the ISO performance. Personally I didn't think it was much better than my old Rebel XT. So when I made the jump to the D7000, I was like
wwhhhhaaooooo what witchcraft is this?! Going from the D7000 to the D700, my reaction was not as profound.
Sadly I had to give the camera back to my photography prof. I might try her D3S next.

At this point I'm still kinda on the fence, I do want to go FX, don't have money nor the desire for the D-single digit line. Even the D700 is slightly big for my tastes. But I LOVE LOVE LOVE its AF. I want to see what the D800 is, it is rumoured to be smaller than the D700 which is a huge incentive.