Why did Microsoft decide a new UI was needed? Why now?
As Microsoft has added more and more features and functionality to the applications over time, it has become harder for people to find the things they want to do with the products. For example, Microsoft Word 1.0 only had about 100 commands, and by using the menus, you could see everything you could do. Today, Microsoft Office Word 2003 has over 1,500 commands, many of which can be difficult to find. That element of discoverability is just one of the key issues addressed by the UI.
