Unfortunately, Open Office is not quite 100% compatible with Micro$0ft Orifice.
If it was, M$ would be out of business on this product.
It's all driven by whether other people, particularly people working in what I might call "fancy corporate environments", are sending you documents for review.
If not, i.e. if you are generating documents to be read by others, then Open Office is just fine, because M$ Orifice will open its documents OK,
AFAIK.
If others send you documents which you just need to read, you can use an old copy of Orifice (say 2003) with the M$ Compatibility Pack, to view them.
But if others send you documents which you need to edit and return, then you have to spend the $$$$$
In my case, when I get a .docx, I quite enjoy emailing back saying "we not not have the latest version of the Micro$oft software used to generate this document"