I should say that I am also tempted by the NEX-7. But it will not be available before the end of the year at the very earliest.
Why the NEX-7? The main advantage for me is that it is a small camera with a decent viewfinder. With age, I suffer from presbyopia and find looking at a screen held in front of my face difficult without glasses. It is better if the screen can be fold out and looked from the top, but I still have the problem that the screen cannot be seen in bright sunlight (although my camcorder proves that a LCD screen can be constructed to be seen in sunlight, I don't know any camera which uses a screen of that type).
If one wants a viewfinder, the choices are suddenly much smaller. I have looked at the Panasonic GHx line, but the cameras are bigger than what I want (especially because the viewfinder rags out of the back). I have also looked at the Olympus external viewfinder, but it changes the camera from small and neat to some kind of cyborg with an inconvenient wart on the top: it does not fit in my pocket any more, nor does it fit conveniently in a bag, etc… There is another inconvenience: the viewfinder is simply a copy of the external screen and you have the choice of having a picture devoid of any information (not even speed and aperture) or having your finder cluttered with silly symbols all around it. I hate that. Sony implementation appears to be designed like a real finder: you can have it show the uncluttered picture with speed and aperture under it.
What is nice about the Olympus finder is that it can be tilted. What is also nice about Olympus cameras is the built-in stabilization.
About the NEX 7 finder, I have seen the identical Sony finder from the A77. The Sony finder is much, much nicer than the Olympus finder, which used to be the best electronic finder on the market (the Fuji X100 finder in electronic mode is similar to the Olympus). It has very pleasing colors (warm and saturated… better than reality). It is a bit like looking at a good LCD monitor. It does not have the "rainbow effect" artifact of the Olympus or A55 viewfinder (the effect comes from the sequential display of the colors on these finders). I has a higher dynamic range. Still: it is far from a good optical finder.
Trying an electronic finder in real use, I found that:
-they are a bit too dark in bright sunlight (but still much more usable than the screen)
-they are far too bright at night and blind me.
If you want to use a manual focus lens, the NEX series has a "peaking" mode which makes focussing a breeze (I knew that from video cameras). But I am not convinced that many manual focus lenses are useful on that camera, except maybe some M-mount 35mm: with the adapter adding extra thickness, the whole system usually becomes quite big, which defeats the purpose of the camera in the first place. And of course, since it is an APS-C sensor, you won't find a wide angle (but the NEX 16mm pancake is better than its reputation).
Maybe the solution is simply to use your D700 with a nice 35mm or 50mm prime until Olympus makes a camera with a built-in finder (but they may go bankrupt and never do that)...