Hi Kirk,
Yes, I am on a Mac but I'm not using Apple's IQ rendering in PM.
If I shoot a NEF and JPEG pair in camera then NX2's rendering of the raw file will (visually at least) exactly match the JPEG when it's opened in NX2, suggesting there's no difference between the in camera JPEG rendering and NX2's rendering of the raw file in terms of colour. Additionally, If I took the JPEG and opened it in Photoshop it would look exactly the same as it does in NX2. The odd man out in terms of colour is PM.
Although I initially used the appearance of D4 NEF's in my example as that's 99% of what I shoot, upon investigation now I can say I also notice this difference in rendering of in-camera JPEGs in PM too. Apologies for the incomplete information. To my eye, the D4 files rendered in PM look similar to Adobe RGB files with the profile stripped out and opened in an SRGB workflow, flat and a little desaturated. I haven't noticed this prior to the D4 and my best guess was a setting in PM had become changed inadvertently, but I can't see where that could be.
The preferences I can see which could have a bearing:
Raw > enable raw rendering (using Apple's image IQ) - unchecked
Color management > Default ICC profile if undetermined - set to Nikon Adobe RGB
Color manage thumbs for display - checked
Ditto previews
Embed ICC profile into camera JPEGS - checked
Am I missing anything there perhaps?