I'm not usually one that dashes out and gets the latest of anything, as a general rule, so this is all rather new for me!!
I picked up the D600 on reputation alone, about a week ago and my first impressions are quite positive, I have to say.
In terms of ergonomy, it fits my hands as well as the D700 before it, but is noticeably lighter. I'm used to NIKON so the controls all fall where I expect them to. The viewfinder is 100% (or near as dammit) so that's an improvement and the viewing screen is slightly larger than the 3" I'm used to - but it's "slightly" larger - i.e.; doesn't really notice.
The mode selector wheel, top left, now latches - this is a good thing, as does the frame selection wheel below it (but then, that always did lock). The virtual horizon which I like on other models, is simply a graded scale at the bottom of the viewfinder - this is ok for the horizontal but there's no vertical scale, which I think is a shame.
Moving the mode selector to this wheel has taken up the space previously used for the ISO/WB/Quality etc. buttons on previous models so these are now accessible from the buttons to the left of the monitor - again, no big deal, in my opinion.
People like Ren Kockwell bemoan the transfer of the AF selection to the lower left of the body, next to the lens mount - frankly I can't see that it makes a great deal of difference - in fact it seems more logical to group the controls for the AF in one place. Another thing he goes on (and on, and on, and on) about is the choice of user specified settings buttons U1 and U2. In the past we had 4 separate groups, all programmed from the rear menu, as these are as well, but they had to be selected from the menu display, as opposed to turning this wheel. I use basically two setups, so it makes little difference personally.
Trap doors instead of floppy rubber to cover the HDMI/USB etc. ports is a great improvement, although there's still no lock or latch on the door giving access to the memory cards.
This model has full HD video - whatever floats your boat - I have enough difficulty with still pictures, so video is a definite no no for me - but I'm sure some will like it.
I often take long exposures, so for me the inclusion of a rear blind would have been nice - but instead I've got a nice little piece of easily lost plastic supplied with the camera - cheap.
As a general rule I shoot landscapes, so there's not much moving in my viewfinder - the following images will confirm this - the AF seems to be as reactive as any of my other camera bodies, and as I generally shoot on A I'm not going to much use discussing the pros and cons of the SCENE or AUTO modes. Sorry.
The shutter is VERY quiet, compared to what I'm used to, and seems very fast - a strange thing to say, but sometimes shutters sound like shutters, a bit clanky - this one sounds very 'clean' and precise.
Still early days - I'll gladly answer any questions as I'm sure there are stacks of things I've forgotten.
Here are a couple of recent images taken with the 20mm AF-D
And one from an hour ago (Friday)