I am generally skeptical about new versions of software. If I have been productive in the version I have, why would I need a newer version? Usually it seems that it is just a money grab by software vendors. In the case of Office 2007, I was additionally skeptical about the replacement of the menus with ribbons. This was partially based on the new Internet Explorer 7 design, which I do not like.
Just by chance, today I picked up a copy of PC Magazine's January edition (so I could read it on the plane), and it provided a First Look review of Office 2007. Ironically, I also happen to be listening to an older (Nov 7, 2006) podcast from PC Magazine (called PCMag Radio), which happen to also review Office 2007. In listening and reading, my opinion began to change. If that wasn't enough, today Walter Mossberg of the Wall Street Journal also released a favorable review of Office 2007.
All the reviews promise that the changes will be difficult to make for current Office experts, as the interface changes so drastically. The good news though is the improved functionality. I believe the improvements in charting (Excel) and formating (PowerPoint) alone are worth the change. Excel will also let you make changes while you preview.
If you want to see, read and/or listen for yourself, check out these reviews: