I think Microsoft is on the right track with the changes made to Office 2007. Processing power and screen real estate have increased, and a more expressive GUI is a natural consequence. Why hide functionality in drop down menus when you have space to show it? Showing more information on the choices we give users, is probably a good idea.
Even if you do not want to design you application to look like Office, there are lessons to be leaned. Office 2007 shows how a GUI can be specialized to fit the characteristics of the application. The ribbon might not be a good idea for all types of applications, but for Office it is. Making you own framework for the GUI, instead of relying on the standard menu bar and the toolbar, might be worth considering. You can make something not looking exactly like all other applications, and get away with it. You might even end up with a better product. Personally I believe OpenOffice will look outdated when Office 2007 is released.
I wonder how easily the new GUI framework for VisualWorks, "Pollock" will allow customising your own GUI... My guess is that Pollock will be very good for making new widgets. Widgets look and feel are all implemented in Smalltalk, and you can easily customize an existing one, or make a totally new widget. I guess making something like the ribbon would take a lot of work, but it could be done. I also hope that I can easily customize menus to contain more detailed information.
Pollock does not fix all problems in the current VisualWorks GUI. For example, window styles are not enhanced by Pollock. Luckily, other projects following Pollock will address these issues.
Currently, performance of Pollock has been varying. This is certainly not a concern now, as Pollock is still in beta. However, having a responsive GUI is very important:
From the perspective of the Office 12 new user experience, performance is critical. The very visual nature of the Ribbon, with lots of galleries and Live Preview, lends itself to experimentation. (…) In fact, we've noticed a profound link between performance and usability; some usability tasks that totally fail when the interface is laggy and lethargic suddenly do great once the software is responsive enough.
Previously there has been focus on how Pollock will make sure the GUI looks good, by ensuring screen updates do cause flickering. Pollock definitely also need to have focus on drawing speed.