Regarding the criticism that IE9 has adopted a browser/OS-specific approach to this: apart from the obvious reason of a lack of a suitable standard for this, the tags as described in the article are not the only way of getting jumplists to show up.

I haven't really tried to figure out what heuristics is used, but most pages that you pin to the task bar will receive some sort of jumplist even if none is explicitly defined. It is comparable to Google search results which, for some sites, add a little table of direct links to site subsections below the result. The new meta-tags are not required for this new feature of IE, and simply provided for developers who want to have more direct control over how their sites are represented if visitors pin them.