The problem comes in the implementation. The graphic design is just horrible. Where is the grid? Where is the white space? What the hell is that round button that replaces the file menu? The title bar just looks awful.
If they could clean it up graphically I really think it could be just as nice as anything on Mac OS X. Ask yourself this, if Apple had come out with the buttons on tabs in the exact same groupings but done it in a gorgeous way, who would be complaining about it? We'd all be heralding it.