You may hear from "Microsofties" who claim that OpenOffice just doesn't render Microsoft Word documents properly. In my 6-7 years running Linux at work, I used OpenOffice exclusively to write and edit documents, and to create and modify spreadsheets. I never had a problem exchanging documents with others. Of course, I was careful to save documents in the Microsoft Word "DOC" format, and spreadsheets in the Microsoft Excel "XLS" format.
It's true that sometimes Word will fail to render a document properly. But it's not the fault of OpenOffice - sometimes, Microsoft Word fails to properly display other Microsoft Word files. Just this morning, I saw an example in action in a meeting:
Last night, one of the attendees sent out some notes for us to read before the meeting. We all dutifully printed out our copy of the document, and brought it with us to the meeting.
Despite the fact that the document was created with Microsoft Office, and that we all run Microsoft Office, there were 3 different versions of the printed document at the meeting. You could tell by looking around the table that one version of the notes (printed from Microsoft Office for Macintosh) arranged the text around a table in a weird way. Another version (printed by Microsoft Office 2007) put a page break in a different place and put an extra blank line between a table and its caption. The original version (Microsoft Office 2003) was formatted as intended.
This was a simple 3-page document in "DOC" format, with an enumerated list of paragraphs, so it didn't take long for us to realize our copies printed out differently, and to figure out the correlation between versions of Word and how the document printed out.
I think it just goes to show: if you have a document that absolutely must preserve formatting, send it as a PDF.