In a large corporate environment, you may have little choice--they locked themselves by cheerful productions of non-portable forms, templates, visual basic-driven web pages and other MS Office-bound "tools". Perhaps a more adequate name for propriatory software would be "lock-in software"?
In a smaller environment, you can use OpenOffice.org suit (OO) that runs on Linux, MS Windows, Mac, Solaris (and more), with full file-level compatibility. It can be downloaded and installed for free (no restrictions whatsoever) so nobody should really complain about the file format (some control freaks still will). Just to make sure, OpenOffice can import and export MS Word and Excel documents of reasonable complexity very well. The native file format in OpenOffice is fundamentally much better than Microsofts (plus it is non-propriatory). Feature-by-feature, OpenOffice can do almost anything MS Office can, plus some extras. Depending on whom you ask, the ease of use varies between "50% more difficult" to "20% easier" (measured on a sample of experienced MS Office users). Very complex documents are best transfered as *.pdf, and OO can make them on the fly.
So, probably you do not need MS Office any more. Download your OO for MS Windows and/or Linux at: http://www.openoffice.org/
Latest MS marketing joke: "Wait, don't install OpenOffice. Microsoft is ALREADY working on a file format that is based on the same principle as that OpenOffice is using. Microsoft will even extend the file format to make it even BETTER." Well, we do not need a better format. We need a open-standard file format.[an error occurred while processing this directive]