Whilst the Kenko is not a bad teleconverter according to many people, I had one and was not happy with the results, so there may be some sample variation. I would suggest you go with the Nikon tc-14e if possible
I use the Kenko Pro DG 300 1.4TC with my 300 2.8 with great results with both my D2x and D3. I have even used the Nikon TC20EII with the 300 2.8, and on the D3, I get fantastic results with that combo as well.
Tested both the Kenko DG and Nikon 1.4's on my 200 f2 VR/300 f2.8 VR. Nikon won hands down.
It's the edges, man. With such great glass what are you really saving here folks?? Of course, YMMV
The Kenko can be used with more Nikkor glass, I'll give ya that. :biggrin: