Blender's UI is pretty good, much better than it used to be. It takes some getting used to, but once you learn the keyboard shortcuts, it's pretty quick to navigate.
That said, Andrew Price's improved UI mock-up did look pretty amazing, and I'd love to see something like that.
E: After watching it, I have to say it has a lot of good ideas, although the dynamic ribbon stuff is probably too much (how did I get here, how do I go back?)
I took two attempts to get the hang of Blender but the UI was so alien I gave up. Maybe I'm going to try a 3rd time because Blender is just such a powerful tool, but I'm not doing 3D full time so it's difficult to justify 3+ weeks learning.
For casual 3D work, I've always been a big fan of SketchUp, but there's nothing like it for Linux. A couple years ago I tried to run SketchUp via wine which to my great surprise almost worked, but when I wanted to save my model it crashed :(
That said, Andrew Price's improved UI mock-up did look pretty amazing, and I'd love to see something like that.