Today I did some tests on how Office 2003 is usable with SharePoint 2010 (one of my customers plans to use this combination). I have searched Google for a while, but I didn’t find any information, what would happen using this configuration. For this test I used a Windows XP client in my test domain and installed Office 2003 on this machine.
Very important in the SharePoint site: when adding a document library to a site, select to use Office 2003 templates for this library.
Creating new documents works fine, when the template of a library is in the Office 2003 format. When we have mandatory columns in our library, a dialog box appears, when we save the document. Also editing existing documents works as expected. We have the same behavior when we use the check out and check in functions. Also a mixed environment with Office 2003 and Office 2010 works fine, when all documents are stored in Office 2003 format.
So, using Office 2003 with a SharePoint 2010 farm works well. There is no need to upgrade the clients to Office 2007 or 2010, but I would recommend upgrading the clients after installing the SharePoint 2010 farm.