It has style aids and allows you to set tone goals. It's not an automated tool which just processes and gives out a "fixed" version.

It gives you suggestions, and marks your errors. It's up to you to decide which ones to add, which ones to ignore.

I generally use its punctual help, and want to see its suggestions about my sentence structure and flow, since English is not my native language.

Also, I use its advice on different levels depending on the recipient of the text I'm writing, plus the length of the text itself.