Just so you know, Office 2007 (in classic Microsoft fashion) saves files in a new proprietary XML format (.docx for Word files, for example) that's not backward-compatible with previous versions unless you do a "save as" in the old format, or unless the person trying to open it in an older version has already installed Microsoft's "Compatibility Pack."
http://support.microsoft.com/kb/924074
If they have a Mac, they can forget opening the new format files unless they have Office 2004 (and even then the converter's still in beta testing and buggy as far as I know), or wait until Mac Office 2008 comes out. Or, if they have Apple iWork, they can open the files, but some of the formatting doesn't work right.
I get Word/Excel files from a lot of different sources every day at work, and it's already a headache.