I take a quick break from reviews, to address another issue. Full Frame. A friend of mine asked me the other day, "Should I get a used D700 or a new D7000?". I was staring at him for a few moments, then I realized: He was being serious!
Full Frame is clearly superior in low light. But does that mean everyone needs it?
Arguably #4 and #3 are somewhat acceptable. Sure, you sooner or later get used to think differently (depending also a bit how much time you've spent with DX). And OK, your 200mm lens is no longer 300mm, like in DX. I suppose you can deal with that, as well.
$2000 is a lot of money; $5000 is CRAZY lot of money. I don't care how much money you make. $5000 on a camera (which will become obsolete is just a few years) is an utterly mad choice. Period. $2000 for a camera which does pretty much the exact same job as an $800 D300 is an equally lunatic option.
Which brings us to lens realignment. Chances are, most lenses you have right now are DX. You'll have to get rid of them and replace them with FX. Newsflash: FX lenses are much more expensive. Either you'll have to start buying old/cheap/crappy 3rd party lenses (good luck using a 28-200 Tamron) or you won't be able to afford but perhaps 1-2 lenses.
Bottom line: FORGET the FX. If you lust for better noise handling, consider this: From your last 100 photos, how many were taken at ISO 1600 or 3200? If more than 30, then you're doing it wrong. Seriously, getting FX for better noise handling is insane. Do yourself a favor and keep the money. Right now, the D300/D7000 are the very best any amateur needs. (Personally I also like the D2x up to 400 ISO).
The situation hasn't changed much. The issues raised above are still valid, as the new "entry level" (sort of) Full Frame Nikon, the D610, is still an expensive camera. You can find a used D700 at a lower price - and frankly, it lacks nothing compared to the D600. Nothing a photographer needs, that is.