It Had To Happen…
In a Microsoft Office 2003 environment where extra plugins can not be installed*, someone brought in a work-related document that had been worked on using a home computer and Microsoft Office 2007. I was getting ready to leave for a run to the Northern part of the state where an office had lost connectivity, so I could not stay for the conclusion. I would like to have seen how it got resolved.
Note that we have seen some ODF files (and .wpd/.qp* files) as well. By talking to the right people, ODF files that do not need to be edited reappear as PDF files, while editable files reappear in the Microsoft legacy formats that get used within the organization. WordPerfect / Quattro Pro files end up being sent back for export to Microsoft legacy formats. I suppose that we will have to start doing that with Microsoft NXML formatted files as well. If you buy MSFT Office 2007, you may not be able to use the NXML format to send electronic documents to your intended correspondents, such as banks, government agencies, schools, or individuals.
A "permission-oriented workplace", where you do not attempt to do anything you have not been specifically permitted to do. This is different from an "action-oriented workplace", where you do everything you need to do, unless you have been specifically forbidden to do so.