Neil, My D300 shows r06 in every quality setting from raw fine to jpg basic. I bought my D300 in February 2008. Did Nikon increase the buffer at some point? Or is there a setting I'm missing?
edit: I just Googled D300 buffer and found three sources, including DPreview that report r12 in all modes. They were all reported in 2008. Neil, if your D300 reports r17 you must have a hotrod mode. I'll see if I can find it on my camera.
edit #2: I think I found it. I had Long exp NR on. With it turned off I now get r12. Also with HI ISO NR off I get r15.