Will I have any problems sharing files with people running previous versions of Office?
All Office 2000 programs, except Microsoft Access 2000, use exactly the same file formats as Office 97. So, you will have no problems sharing files when using those programs.
Microsoft changed the file format for Access 2000 (the database tool in Office 2000) to bring it into compliance with Unicode and thus add support for new multilingual capabilities. Access 2000 includes file converters so you can freely exchange files with coworkers and colleagues using previous versions of Access. For more information, read Microsoft's Office 2000 and File Sharing in a Heterogeneous Office Environment white paper.
Another file-sharing enhancement is the new Save as Web Page feature, which enables you to share your documents with anyone, anywhere—regardless of the type of software the other person uses. For details about this feature, visit the Web Lifestyles section of Microsoft's site.