You can keep your money, Sue. Mr. Gates has more than enough already, and he's even provided a free converter that will let Office 2004 programs (and even the older Office X from 2001) open the new file types that Office 2007 for Windows and Office 2008 for Macintosh create. You can get it from:

http://www.microsoft.com/mac/downloads.mspx?pid=Mactopia_AddTools&fid=EDB6CD8F-832C-4123-8982-AC0C601EA0A7#viewer

The only reason, in my opinion, to upgrade to Office 2008 is if there are any new features you think are worth the expense. With that converter installed, you can keep using 2004 just fine. In fact, a lot of Mac users who've bought the new version are not at all happy with it. It was touted as being a lot faster on Intel Macs, but it's not. To the contrary.