2. This is a bit to general and without references to make it a real argument
3. It doesn't take much more space than the classic menu bar a few rows of tool bars which you needed to have most of what you needed one click away.
4. Well yes. But I think it's better this way then having a huge code bloat because you have to maintain 2 UI.
The main advantage is that the information stored in the ribbon is much more versatile than simple buttons and a few combo boxes.
On the other side it's good, because if everyone thinks like this, LO may get enough attention to beat MS office. ;-)