What is the problem with Microsoft Office Ribbon?

I had some issue with Microsoft's Ribbon interface (first introduced in Microsoft Office 2007). Actually, I think many people had more or less trouble using it. So I was thinking how to sum it up, what Microsoft did wrong, and where it placed its risky, but reasonable bets that might seem wrong but a necessary to obtain long-term viability of the product:

• Incompatible with previous knowledge - actually this is not up to Ribbon, but to its implementation in Microsoft Office 2007. Microsoft just changed some of its classifications of Tools, as they are not classified the same way as they were in menus and toolbars. I think it was too much to change both things at the same time
• Visually chaotic - again, this could be implemented different way with same Ribbon technology, but it seems that at this moment Microsoft prefers this implementation. So, while I think it is a good thing that some icons are bigger, the way of their layout on Ribbon makes you feel disoriented. Over the time, your spatial memory will probably get used to it.
  
•  Non efficient for using rare options - menus seem to be better here. If you go for some option you just need at that time, and it is not a rare user pattern Ribbon doesn't do well. It doesn't come back to most frequently needed tools, but it leaves you on some special toolbar you might not really need. So, you must click to go back where you want. It hurts productivity. Even if you get used to it. And it will help you not to want to get used to it.

 

 But the real gain is in Easy access to a lot of tools, specially the ones that you had to go through dialogs to use them, and you have them at a touch of the hand.