Today finally I got my hands on Visio 2010 ribbon.
It really works! IMO, the ribbon is awesome from the developer's point of view (and hopefully from user's point of view too) - it seems to include "everything I ever wanted" from the user interface as a developer. The above articles do work with Visio just fine; i.e. one can use these as a reference to work with Visio ribbon as well. It just works!
Though, I've got some issues.
I haven't figured out how to do the shape context menu customization. It seems that the "old" techniques for accessing the context menu like (commandbars) -
CommandBars("Drawing Object Selected") or (uiobjects)
ItemAtID(visUIObjSetCntx_DrawObjSel) ceased to function (?!). Instead, they do something weird "on my computer" - they add a top-level menu to the tab "Add-ins" (?!) As if the "Drawing Object Selected" is not recognized as a special command bar name anymore (?!). Or probably I have messed up somehow... Anyways, unfortunately I was unable to change the shape context menu in new Visio. No luck.
I needed to customize the context menu to make a
hierarchical shape-dependent context menu. Fortunately enough, Visio 2010 seems to (finally!!!) include the "natural" support for the hierarchical shape context menus in the shape-sheet (via new column "FlyoutChild" in "Actions" row).
Viva la visio developers!
Second, I've got a question - do I understand correctly, that from now on Visio shall support the Custom Task Panes, like all other "ribboned" office applications do? Am I missing something? My CTPFactoryAvailable is just not called! Or do I expect too much?

All other things I needed can be done in "no time" -
- Creating ribbon buttons
- Creating ribbon menus
- Setting custom images for menus/buttons
- Enabling/disabling controls at runtime
Definitely, this ribbon opens a new horizon for user interface customization! Now Visio UI customization became really flexi'ble (c)

- Now one can use three (!!!) mutually exclusive approaches for that - UIObjects, CommandBars, and the Ribbon. I just wonder how many customization approaches will Visio 2020 have?

BTW, one can visually design a custom Ribbon using Visual Studio ("Visual Studio Tools For Office" have a special designer for that). Though AFAIU it is intended to be used for the "tools-for-office"-based add-ins, the raw ribbon xml description can be easily generated (using "Export to xml" command) and this XML can be used for any type of add-in, not only for the "tools-for-office" addin. I was particularly interested in the native code - it works just fine.
Kind regards, Nikolay