I have no idea whether this is the right forum, but wanted to share my thought process with others. I'm on the wait list for the D600 at Berger Brothers - the same place I got my D800E.
I shoot a lot of IR with a converted D200. Rather than converting an existing D300 or D7000, I am going to convert a new D600. The thought process is that most of my IR work is landscapes and architecture - and these subjects are great with the larger FX sensor and large number of pixels. The rumored features of the D600 appear to line up pretty well - it's new technology and probably cheaper than a used D700. And it will share a common battery and accessories with my D800E and D7000.
There are certainly some reasons to go with a D700, but the larger file size of the new cameras is a real plus for landscapes and IR. And the D700/D3 has a light leak issue for IR at higher ISO levels (above ISO 1600).
#2. "RE: D600 - on the wait list" In response to Reply # 0
I think your reasoning for getting a D600 (assuming the rumored specs are similar) for an IR conversion is sound. Of course, your path would be one of a double early adopter. You will have the D600 before almost anyone else and presumable be one of the first to IR convert it (which would essentially void the warranty). You mention the D700/D3 has a a known (but minor) issue for IR conversion. What will the D600 have?
#3. "RE: D600 - on the wait list" In response to Reply # 2
<You mention the D700/D3 has a a known (but minor) issue for IR conversion. What will the D600 have?>
According to a Lifepixel video, there is an IR light used to make sure the shutter speed is correct on the modern cameras. When you remove the IR filter, at high ISO levels you get some light leakage. This is not a frequent problem as I don't normally use an IR camera in low light - but I have done that some. The D7000 has changed the wavelength of the IR light to above 850 nm - and that apparently resolved the problem. I am not sure what they did on the D800, but I am guessing the higher wavelength will be used on the D600. If not, it is only an issue at ISO 1600 and higher.
Good point on the warranty. That means I'll need to test the camera pretty well before investing in a conversion.