As you can see above, the ribbon is task oriented making it more discoverable and easier for new users to get acclimated. As objects are selected, the ribbon dynamically changes presenting the appropriate tools associated with modifying them.
Another significant change to Revit this year is the new conceptual design environment. As described in the Help menu, "It is a type of family editor that provides sophisticated modeling tools and techniques for designers to create massing families". It is a free form 3D modeling environment that feels very much like Inventor.
Revit Architecture 2010 is packed with lots more new features and I encourage you to get it loaded and try them out. Some of the things you'll find is improvements to interoperability, worksharing and much more.