This was recently described to me as follows: One can actually become more efficient at typing by typing fewer of the letters of the word, and letting the auto-correct find the right word. One does not have to hit the keys exactly, but rather, one can get pretty close and still get away with typing only about 2/3 of every word that one needs.
My sense is that lots of people are getting very good at this. It's dicey, and there are errors associated with it. But in the end, if you can cut your typing time by 2/3, you should! And those who do, will be faster and more efficient.