My turn to add the "ME TOO" to this thread.
I took the plunge and got my D600 early in the new year. Unfortunately work has been silly-busy so I still only have 350 photos worth of experience. LOVE the difference a full-size sensor makes to my depth of field and wide-angle framing (I suspect I may not be quite so fond of the "shortness" I encounter when I go out to 200mm though). LOVE the virtual horizon for my landscapes once I worked out a shortcut to it. The size fits my little hands perfectly. I've paired it with the 16-35mm f/4 to start with and am really enjoying the camera-lens combo. The only negatives so far... I find the focus area a tad small. I'd read in the reviews that it was from the D7000 which I'd played with and liked, what I didn't consider was that it becomes a smaller area on a full-frame. When I'm shooting wide angle on the tripod I'm using hyperfocal distance so won't have impact; but it will be a bit more limiting with the dog photos. But still, more cross-sensors than the D90, so still more flexibility than I'm used to. The second negative is that I already have the dreaded dust bunny problem
I'll be living with that for a little while as I'm not quite ready to send it away just yet. I've attached a couple of images from my first two outings with it.