Ever since I have discovered Grammarly, I have never let it go, as my grammar is so bad and thanks to Grammarly it is bearable. Grammarly helps improve communication and writing by 1000% and for me, it is a must tool!
I do not just recommend Grammarly, but I force people to use it, especially people like me with not perfect English grammar. Their free version is sufficient enough to improve writing and with the business plan, you just rock like a professional writer.
There is a small issue with odd words and some names as it can show it is wrong which could be a bit distracting and even thou you use feature ignore it, it still pops it up.