Office 2007 is a mixed bag or tricks. Some of the system is great and other area’s are just too different for people to want to figure out and use. I love Outlook 2007 and cannot live without the real time searching, but there are still simple things I used to do in Word, that I have no clue how to do in Word 2007. Oh well that is my problem to figure out, but above and beyond the usability issues of the programs themselves, a bigger issue is that Office 2007 uses a new file format structure and something saved in Office 2007 will not work in the older versions of Office. This can be very frustrating having worked on a document and saving it just to have another use not be able to open the document at all. Then you need to re-open your doc and save it as the older version of Word and worse, remember to do that each time you create a document.
Luckily, Microsoft has learned throughout the years that nearly no one converts all of their users to a new version of Office at the same time so they create software updates for older versions of Office that can deal with the new versions of Office. If you have any users on Office 2007, it might be a good idea to install the Office 2007 Compatibility Pack on the users who are not working in the Office 2007 programs. This could alleviate a lot of future headaches when it comes time to sharing files.
Give it a try!