I like the exstention, tough there is one flaw I've noticed when Using it with Firefox...
If I right click on a word that Grammarly selects to "correct" it there is a 70% chance that the word isn't changed but gramerly pastes the correct spelling at the location where my cursor is... this isn't useful at all (example, I write "hello, how is you day going" and it should correct you to your, if I would correct that after typing going grammerly would change it to "hello, how is you day goingyour" :/)