I'm not an office user and hopefully never will be (
OOo for ever yo!). But whenever user interfaces and keyboard shortcuts are being talked about I always think of the 3 CAD/Modeling programs I was using for a while.
Rhino is pretty traditional at first, except it uses the right click button extensively. It's interface is completely customizable, you can control what each button does (both left and right clicking), if it has a sub menu, what the button looks like, how big they are, create/delete buttons and sub menus, put them anywhere, etc. It's awesome! Oh yeah, the keyboard shortcuts are customizable too. You can jump right in, or customize the crap out of it if you want. Every program should be exactly like Rhino3D!
Maya forces you to have a 3 button mouse (you can't use Maya without it) and you must have your left hand on the Ctrl, Shift, and Alt keys at all times (again, these keys are used constantly). The keyboard/mouse button combos are confusing and not intuitive (IMO at least). It's possible it's customizable, but I doubt many people do.
Last is Lightwave3D. They took all the UI conventions and threw them out the window. The thing is, they did an amazing job! Undo was changed from Ctrl+Z to just U, Redo was changed to Shift+U. Revolutionary stuff! The learning curve was high, but once you got it it's gravy. Everything was customizable, but to do so would take forever...
Sorry to talk about non-ribbon programs so much... I guess what I'm trying to say is, from what y'all have said, it sounds like MS might have something that actually works better but is going to be harder to learn in the long run. I'd stick it out.
I thought the same thing when I heard you can't put the ribbon on the side: Um, hi idiots, widescreen monitors are
in in a big way. That big thing on the top is going to force people to write in an anamorphic workspace. Which, appropriately will make the font look like it does in the movies... 56pts.