This is a very succinct post...
If you have any recent Nikon long glass, AFS or the older AFI, and you need some more reach, or want a narrower depth of field, or apparent closer focussing, get this. Ditch any other 2x 'converters, including older TC20E versions, because this makes them look like bottle-bottoms. It's that good!
Like all the TC-E converters, it will only mount onto certain lenses - basically that's AFI/AFS types from the 105VR, 70-200/80-200AFS, then 200/f2 and up. It maintains full metering with all such lenses, and will still permit autofocus with the f2.8 lenses - like all 2X teleconverters it robs the lens of two stops of light, f2.8 becoming f5.6 etc.
(NB. although Nikon state the minimum aperture for their AF system to work is f5.6, in good light I have seen that it will allow focus with f4 lenses - effective f8 - but probably not to be entirely relied on).
Briefly, it gives very good results wide-open, and improves further stopped down one stop. As is usual, the reduced maximum aperture does make the AF "think" a little more but it remains effective and surefooted, and the VR works as normal. It's a bit pricier than the other TC-E models, but much cheaper than owning a 400+... Certainly I find that the 300 f2.8VR plus TC14EII, TC17EII and the new TC20EIII covers my needs well enough now.
This isn't a company buy - I stumped up my own cash for this, too!