This phrase is sometimes translated as "translator, traitor!" Too many times in the past, a new version of a product not only does not care about the previous version, to the extent that it considers itself as "innovating", wants new users to put the hate on the old product.
Love it, hate it, Office 2007 is different from Office 2003 and your users may have trouble at frist making the switch - "translating" how they used to do a thing into the new UI. Show of hands - how many of you have gottent the question " Hey, where did they put the <foo> button?"
Here is the Office online URL you can send to your users that allows them to get the translation from the old "way they knew how to do it" to the new way: http://office.microsoft.com/assistance/asstvid.aspx?assetid=XT100766331033&vwidth=1044&vheight=788&type=flash&CTT=11&Origin=HA100744321033.