Ribbons are great bits of User Interface in many cases, and Microsoft nailed it with the keyboard interface. (Tap Alt, then tap the keys indicated on the ribbon you get to the command you need).
Revit's ribbon implementation works well until you hit missing/broken keyboard shortcuts.
Example 1:
Tapping (Alt, G, OB) should open Object Styles. Instead it opens Location Weather and Site (Alt, G, O).
Example 2:
Tapping (Alt, G, AS) should drop down the Additional Settings submenu. It does nothing.
Example 3:
The Select pulldown below Modify (Alt, M, X4) has keys for all of its sub-items, but
Manage > Coordinates (Alt, G, C) does not.


See also Insert > Insert from File, Annotate > Keynote, and many others.