This is very important -- maybe more important than the file compatibility issue. Your mind and your fingers have been trained for years to navigate well-worn paths to cause things to happen that you need to happen, and many things are now different.
I also find that Office 2007 exposes many more options at once in the Ribbon, and that is not always to the benefit of productivity.
I guess it's possible that someone starting from scratch, having never used Microsoft Office at all, might reach a higher level of productivity faster with Office 2007 than with previous versions -- assuming you need on average to use advanced functions.
I'm willing to concede that that's possible; however, I don't personally believe it.
/rich
Be aware that the menu organization is *very* different. It took our
groups (TAP and TGS) around 2 weeks before their productivity was back
to 95% of pre-upgrade levels (and the complaints stopped).