This monday I had to review and extend a proposal in a docx format, which is one of the rare cases I need an office suite for the job. After hours of writing and commenting, I sent out the proposal to the project partner, who said he could not open the document at all. Turns out, libreoffice failed to properly save the document.xml, so that even libreoffice couldn't re-open the file itself. I had to put in extra hours and fix the document until late in the night by copy pasting parts of the broken XML or rewriting small bits. That was the last time I will use libreoffice.