Thinking about User Interface

Zack Whittaker is doing an interesting experiment that is going for 48 hours fully Open source. That got me thinking about the Office suites issue. Being extremely simplistic you can either go for Microsoft's Office 2007/2010 or go for OpenOffice 3.2 (I know on both ends, open source and propietary, there are lot's more suites and those will also have part on this post).
The major difference between this two suites is the User Interface, on one hand we have the office fluent interface (a.k.a Ribbon) and we have on the other hand the old icon and toolbar based aproach of OpenOffice (and most of ther office Suites). reading about OpenOffice's Rennaissance project got me thinking what would be the ideal User interface for an office suite, taking into account all the functions this type of programs have and what are User Interface paradigms that were a good option in the past but nowadays are old fashion.

When you get to think of that you see some new User interface ideas that have started to take shape, one of this is the removal of the menus on top of programs to be replaced by other type of functions (Windows Vista/7, office 2007, Google Chrome, etc) the minimalistic approach of some other programs, like Google Chrome, you see they are fond to the users, 'cause user just want to work on the stuff the program is supposed to do and not be bloated by all the characteristics the program has to offer.

Taking this into account, what would be your ideal User interface for a Office suite? Which rules should you follow?, which should you leave behind?