Getting harder to transition from mouse to keyboard
I find that the switch from drop-down menus to ribbons in Windows software doesn't help. With the menus you tended to have the shortcut displayed alongside the text in the menu, so common ones would eventually start to register without actively trying to learn them. Other operations I'd find myself navigating the menu via the keyboard, for example I couldn't tell you if Word has a keyboard shortcut to Insert a Picture from a File, but I know Alt+IPF will do the trick.
With the ribbon I don't find it nearly as natural to pick up shortcuts this way, I actively have to look to see what they are.