First, I want to thank the members of this forum for all of their useful advice and answers to my questions about sound recording when using my DSLR.
I just purchased a Sound Devices SD302 to use with my Nikon D3s and it's terrific! I have posted a brief comparison of recording directly to the D3s recorder using several different methods: using built-in mic, using rode ntg-2 into the D3s, using rode ntg-2 into the SD302 then the 302 into the nikon, and using the rode ntg-2 into a zoom h4n then into the nikon via the headphone output of the zoom.
The test is assuming that one is doing a run and gun with the mic on the camera (not ideal, but practical). I am working on comparisons with the mic closer to the subject and may try to post those as well.
I've posted the results here:
http://www.youtube.com/watch?v=jsOU3CWO7t4Bottom line: the SD302 works very well with the Nikon. I set the output attenuation on the 302 to -40db, set the Nikon audio to manual level 1, and run the meter levels on the SD302 at around 14-16 and it works very well.
Hope this is helpful/interesting.