I get a lot of questions about how Office 2003 will integrate with SharePoint 2007.  Your best source for this kind of information is the Microsoft Office Programs and SharePoint Products and Technologies Integration – Fair, Good, Better, Best whitepaper.  You can get it here:

http://www.microsoft.com/downloads/details.aspx?FamilyId=E0D05A69-F67B-4D37-961E-2DB3C4065CB9&displaylang=en

Office 2007 is by far the best client to use with SharePoint 2007.  I plan to blog with some additional information that isn't in the whitepaper.  Stay tuned.