The quality of the document they send me back is very professional. Everything they corrected is annotated and highlighted in a very clean format and easy to follow what has been changed. They don't just only correct grammars but also give some comments on sentences that need to be clarified or developed for readers to understand. It is really helpful to gain some insight into the contents of writing. And the online customer service is very friendly and helpful. I am 100% satisfied with the service and will continue to use it. As a non-native English speaker who works in US, this kind of easy and fast proof-reading service is what I always dreamed of. Only thing I wish is that I want to see who's reviewing my documents, because I want to thank them but I have no idea who it is. For other online proof-reading service I could see their profile and pictures. That will give me some more personal touch.