I like that it is very easy to start using and to learn, and the more that I use it, the more I am both impressed and liking it.
Nextcloud integration with OnlyOffice Integration Edition works like a charm. Office Documents compatibility is quite good and concurrent editing is really appreciated here.
My overall experience with Only office is good. Our organization mostly have Linux systems installed so it's a great help to us.
It is not fully compatible with Microsoft Office. Docx, I had bad surprises on complex documents and was forced to use Office online.
The bad thing is that I need more space for it now and have to fill in a review.
It was a real problem when I made a presentation with LibreOffice at home and then presenting at school with Powerpoint.