Rating this one is a little hard because there is definitely room for improvement, but it's a great start and you can't beat the price!

I have listed some of the cons below, but the way I see it, if they keep improving, this tool will soon match or exceed Grammarly and I am happy to have a lifetime deal with three users (so my partner can use it too without paying for a second seat), and i will never have to pay annual fees again for a spellcheck/grammar checker. I don't think I can really go wrong, because the alternative, Grammarly, isn't 100% accurate either and it starts at $99/yr. So I'm willing to deal with the refinement period.

I will mention some cons that I have experience. But again, take them with a grain of salt, because Grammarly might not be a lot better. Not sure. I didn't like them much when I tried them.

Here are the cons I noticed:
The recommendations are sometimes just wrong because they are not doing well with the grammar in the context of what I am writing. For example, I find a lot of article errors where they want me to insert articles that don't make any sense. E.g., if I said, "you have to put things in context to understand the intended meaning", they might prompt me to insert "the" before context, which is just wrong. Of course, that also makes my stats inaccurate because many of the suggestions that I ignore were inaccurate, but I don't care a lot about the stats anyway. It's more of a nicety.

Also, it catches enough typos and spelling mistakes and little grammar tweaks here and there that I can overlook all the false positives.

It's not too smart about misspellings sometimes--again based on context--but I am not sure that Grammarly is much better.

And, neither of them work great on certain kinds of pages, so they are equal in that capacity.

Conclusion:
I am happy to have purchased this and will continue to use them in the hopes they continue to improve and I've made a good invest at the right time to get in at a great price and reap the rewards later. ;)