I had my T.C. on my camera for some birding. I saw some bumble bees - the big red butted ones buzzing about and thought I should go get my 105 2.8 macro (err Micro-Nikkor) lens.
But I forget to take off the T.C. so what I find is that I now have a 150 macro (of sorts) lens.
As always a teleconverter comes at a price in light (one less F stop) and I.Q. (or so most say). '
But it works. I was shooting bees and they were up to a foot or so away most of the time. Well except for the dead one - that one was maybe six inches away.
Sometimes you need a little more reach.
For comparison here is one shot with the 105mm without the T.C.