We've been playing with Office 2007 at work. I think once I get used to the new UI some of the features will be great. But the UI is going to take some time.
In one of Paul Thurrott's articles on Office 2007, he said "the ribbon doesn't really take up that much more onscreen real estate than does a standard set of menus and toolbars in an equivalent Office 2003 application..." I didn't believe that for an instant.
I don't use an external monitor on my laptop so I'm running on a 1024x768 screen. I've worked to minimize the space that my menu bar takes on Word 2003. Here's what mine looks like:
Count 'em. 77 pixels and I probably counted one or two extra.
Now here's Word 2007:
141 pixels. Waaaay too big for me. That's almost 20% of the screen height.
But all is not lost. Double click on one of the tabs and the ribbon will kinda autohide until you single click on a tab to reveal it. Esc will make it hide again. (Paul did mention this.)
The other issue I've had is compatibility with pre-Word 2007 users. Microsoft has changed the default style and default font. To minimize the grief for non-Word 2007 users, go to Change Styles and then Style Set and change to "Office 2003." This fixes the line spacing problem. Then go to Change Styles and then Fonts and set to "Office Classic." This gets you back to Times New Roman. If you leave it as Calibri, it will look nice to you but comes over to pre-Word 2007 users as a substitute non-TrueType font. Finally go to Change Styles and click on "Set as Default."
Now click on the Office logo and find Word Options down at the bottom. Click on Save and set "Save files in this format" to "Word 97-2003 Document."
Now go enjoy!