I've been spending alot of time lately talking to customers about all the great thinking that has gone into the creation of our new Microsoft Office suite. Being new to Microsoft much of my information and insight comes from my own perspective on good user experience design and from other Microsoft folks. In particular the wonderful blog that Jensen Harris maintains.
Love the ribbon or hate it there's simply no better example of risk taking than what we've done with the Office interface and the ribbon. What's most interesting about Office is how we had to balance simplicity with complexity and we didn't really have the luxury of solving this problem the way a start-up would with a new product (It's pretty hard to strip features out of a shipping product that hundreds of millions of people use.
I'm not sure anybody does a better jobs explaining both the challenges and false dilemmas that are raised by the current simplicity craze than Joel Spolsky in this post.