I have the 1.4 and the new 2.0, and have used them both on my D300 (now gone) D700 (now a back-up body) and my current body, the D800. The 1.4x and 70-200 is a great combo! I used to have the older VRI and with my switch to primarily shooting FX, upgraded to the VRII.
From all reports, the older 2.0 wasn't very good, hence a lot of people going with the 1.7 but when the newer TC 20e III came out, I skipped the 1.7 and haven't been disappointed. I don't usually shoot that long anymore but I've found either of these to work well with the newer Nikkor 70-200.
I can second this as well, I have the Nikon 70-200mm f/2.8 VRII as well as the latest 2x TC and have used them together numerous times when I have needed that extra reach. More so then with the other smaller TC's you can truly see a jump in your reach to a level that, at least I find, to be significant enough to make it worth it. I haven't experienced any issues with Autofocus and it seems to preform just as well but then again stopping an f/2.8 down a couple of stops shouldn't be too much of an issue. Quality wise I have found there to be no noticeable degradation of image quality with the use of this TC. I'm sure somewhere on my Flickr there are some samples, but I apologize that I cannot find a good one right now.
Of course renting is always good before you buy. I can't honestly say that I noticed any significant jump in performance of this lens when I switched from using it on my D3s (now backup) to my D4, it worked just as good on both and absolutely categorically met my requirements. Considering the small size of all of these TC's (the 2x being the largest) and relatively inexpensive price there is really no reason to not have one for when you need that extra reach. a f/5.6 400mm will certainly do in a pinch, especially if you can bump the ISO up without having to worry about noise.