Have very few issues, however nothing is perfect

I love the functions and it works properly most of the time. However, there are times when it slows down and mostly makes a page unresponsive. I understand that it's on beta mode for Google Docs but I never have this problem in Chrome. Only in Firefox.

Grammarly is well worth the low cost for the complete version. It is usually accurate in performing the daunting task of finding and correcting grammatical errors. Its better than most. I use it all the time.