I tried it on some basic essay and the corrections were off. Even when it made a good suggestion, the replacement often got an additional letter with it and I had to delete it. Like many here, I bought this as a Grammarly replacement but it's not going to do that any time soon.

I will keep the product and renew Grammarly for a year, hopefully by then this product has matured enough to be a full replacement. Or if I'm lucky, much sooner.

One last word, keyword density in SEO has been a dead topic for over 10 years. I don't see it as a strong point to check for something like that in SEO.