I upgraded to Office 2007 over the holidays. Overall I think it is an excellent upgrade but not without getting past some challenges, a steep learning curve, and acquiesce to do things the Microsoft way.
Installation was straightforward but it took over 30 minutes on my Dell D620 with 2GHz / 2GB RAM. After installation I was shocked to see that the interface had dramatically changed. I guess I hadn’t kept up with the reviews on CNET. The new ribbon bar looked attractive but also quite large and intimidating. I couldn’t easily find things in their old familiar places that they had been in past versions.
Here’s what my Microsoft Word 2007 menus and toolbars looked like after installation. They had been replaced with a tabbed interface of buttons and menus that they call a “ribbon”.
One of the first things I wanted to do was Print my document. I looked everywhere for the Print option, I looked under ever “ribbon” and option I could find. 
I finally noticed that every time my mouse passed over the icon in the upper left (what I now know is the “Office Button”) that it began to glow. My curiosity was peaked so I clicked on it and another array of options appeared. It was certainly not very convenient or intuitive. This is one of the most frustrating things about the new version, why would they hide some of the most commonly used features under a glowing button?
After discovering this hidden menu I began to click and right-click on everything I could. I eventually right-clicked on the “Quick Access Toolbar” and discovered I could add some additional shortcuts to common tasks like Print, Print Preview, and Email. (Note that annoyingly you cannot drag and drop the order of the items, you have to go to a different screen to do that.) I also discovered I could minimize the Ribbon bar to recover some screen real estate. So eventually it looked like this:
By far the best enhancement (apart from the overhaul of PivotTables in Excel) is “SmartArt”. It is located under the Insert ribbon. It will format any bulleted list into professional looking three-dimensional graphics with an additional two ribbons full of options to format just about any way imaginable.
After a couple weeks of heavy use I believe the new interface is superior to the old. The visual representation of the menus makes it easier for new users and is more efficient once you know where to look. But users familiar with the old way will find it very frustrating to locate certain features. However, the overriding problem still remains. It screams of feature “bloat”. Most of us never use more than 5 – 10% of the features so making the most commonly used features easy to find and hide the rest would have been a far more productive use of Microsoft’s time and efforts.
Curtis S