As far as I can tell, yes — and so is LibreOffice, since people are talking about that one, too. And I suspect they both have the same limitation — encrypted Office files. So yes, I can read .docx, .xlsx, and .pptx files. I can't read Publisher (.pubx) files, but neither can Mac Office users — Microsoft never released Publisher for Mac. I can then write them to the iWork formats. I can also take an iWork document and export to Office. I suspect Office can import iWork files. Office interoperability is mostly a solved problem, though I think there are a few outlier cases.