I'm pretty sure Silicon Valley is just getting started at walking all over this one, and the end results are going to be horrifying. Or maybe just annoying.
I never want something to brightly say "it looks like you're writing a letter", even if it's right. Even if the computer was smart enough to write the letter for me, better than I would have. Even if GMail has read a trillion emails and thinks it knows exactly what everyone's replies should be.
No, just shut up and let me write, let me work, let me live. No, I don't want to have a relationship with a machine. You be the tool; let me do the thinking.
On the other hand, my phone's autocorrect is a nuisance. It's constantly trying to inappropriately switch "it's" and "its" or "their" and "they're", especially when it's the first word of the sentence and the algorithm has absolutely no way of knowing how the sentence will unroll. That's a distraction that has the opposite effect. It makes a greater demand on my attention by forcing me to watch my typing like a hawk to make sure autocorrect isn't inserting errors.