I have used Autotune, but found it a bit of a blunt instrument.
Melodyne is my pitch correction of choice. Not only does it show pitch on a musical stave, but it also tracks the variations in pitch through time on a single note.
It is very common for singers to sing way below the "correct" pitch and slide up to the note during the attack phase of the word.
Most singers have some vibrato, sometimes very wide.
Sometimes these vocal quirks are exactly what makes the characteristic style of a singer. A student of mine once observed that Bob Dylan sang like a Hoover- and in a way he does, treating pitch as a continuous thing rather than discrete notes.
Sometimes however, pitching needs to be clean and vibrato minimal, on harmony vocals for example, and many singers cannot do that.
With Melodyne they can.
I have even, for my own amusement, built up a single vocal line into a complex close harmony piece using Melodyne on my own voice.

Pitch correction is like every other example of technology.

Some people will use it to beat the world into submission.
Some people will try to use it to make the world a better place.
Some people are natural luddites and will hate the very idea.

As Dave MacKenzie shows, the jury is still out on even temperament, after more than 300 years.
We all have our own ears.
Cheers
Dave