If you look at SpaceClaim, SolidWorks, Solid Edge, AutoCAD, Inventor etc. look at the technologies they use, there are common components, many use Parasolid, Spatial etc. to provide their features and functions. If UI design is also standardized, where can the vendors find the room for innovation, for differentiation and how can they truly support the 3D-based design workflow? I guess the answer is that the Devil is truly in the details.
MoI's UI is Cool and thanks to Michael is not Ribbon'ed up. Also one of the most impressive UI designs I've seen is the forthcoming Siemens NX 6. de-cluttered and minimized.