The Ribbon is too big. It often looks stupidly redundant (section titles matching action button titles, like Find/Find and Exit/Exit). Icons are overused; it shouldn't be a sin to let "only" a word be the label for something. Mostly it looks like somebody emptied all the drawers onto the top of my desk, forcing me to stare at a pile of junk all day long even though 90% of the time all I need from the pile is my pen.
"Is there any research or evidence to suggest that the Ribbon is a UI failure?"
"The Ribbon is too big" is not research, and is anecdotal evidence at best. I, too, would love to see some actual research into the Ribbon. Programmers and the like hate it, but what about the "average Joe"?
I agree that the Ribbon is too big. It's certainly not something I want occupying my screen whenever I'm using explorer. Though, when I'm searching for options, I am fine with the Ribbon's presentation. It's fairly intuitive. At least as intuitive as the traditional drop down menu system, though that's probably not saying much.
Fortunately, I believe it can be minimized[1]. I just hope that the minimization carries over between sessions.
