Just starting to work with it--they offer a 14-day trial, so you can check it out yourself. Its capabilities are amazing--I'm using it to automate my paperless workflow as follows:
I download a large variety of bills, statements, etc. from the web. Hazel is able to monitor my downloads folder for the incoming PDFs, and then rename and move them depending on what they are. She can look into the PDF itself for unique information that helps identify what the document is (for example, an account number, a word or phrase, etc.). It has to be a searchable PDF -- she doesn't do OCR as far as I know -- but most downloadable docs are. Further, she can extract information from the document (such as the billing or statement date), and use it in the file name! In my case, a typical file name would look like this...
2018-04-30 - phone company bill.pdf
...where I want the date to be the billing date. No matter how the date is formatted in the document, say it's "April 30, 2018", she can extract it, reformat it, and use it in the file name. After she renames the file, she can then move it to the appropriate folder, all without any intervention from me.
I feel like I'm only scratching the surface of what this program can do!