Calligra can't deal with .docx files at all, and that's enough to disqualify it, really.
I mean, you can save in .docx but you have to manually type in the file ending cause there isn't an option for it.
And it can technically open .docx files, but don't be surprised when it suddenly adds 6 pages to a document that contains nothing but the word "test".
(I couldn't find out if that was caused by the saving or the opening, but it doesn't really matter.)