I'm a D3x user, and am thinking NEX-7 for a small, light travel cam. I've been using the GH2 in that role, and have mixed impressions of it. The resolution is pretty good (not D3x, but then again, what is), but I find the dynamic range lacking - worse than I expected. The video is GREAT (I've used it alongside a Sony EX1, and it keeps up surprisingly well), but the controls are notably clunky... There is no viewfinder on the GH2 that I find really satisfactory - the EVF's colors are way off, and the rear LCD is low-resolution.
The NEX-7 is supposed to improve substantially on the GH2 in the three places where I don't like the GH2 as much - dynamic range supposedly nearly keeps up even with a D3x, the triple dial controls leave everything highly accessible, and the LCD and viewfinder are both superb.
I don't have my NEX-7 yet, and haven't decided on lenses, so what I've got below is what I've managed to distill of others' experiences, not from personal experience.
The problem is lenses - the 18-55 that comes with it is a better than average kit lens, BUT it's a kit lens. The 18-200 superzoom is a better lens than the 18-55, but still not a great lens... The 55-210 is, again, better than average for what it is (a cheap variable aperture modest tele zoom), but nothing special. The 18-55 and 55-210 were both designed for the less expensive NEX bodies, and for users moving up from compact cameras, not for landscape photographers used to superb lenses and looking for a lighter system. The 18-200 was originally designed for the NEX-mount camcorders, and is a great video lens that is a pretty good still lens on the side.
As for the primes, the 24 Zeiss (expensive) and the 50 are supposed to be very nice, the 16mm pancake gets very mixed reviews and I haven't seen much at all on the 30 Macro.
Of course, the NEX-7 is easily adaptable to just about any lens, from 50 year old Olympus PEN lenses to current Leica glass. Except in the case of Sony Alpha lenses, you lose autofocus, and very few lenses (a few third-party Alpha lenses) provide image stabilization, but there's huge choice (some of it truly excellent)...
-Dan