What we’ve done is moved all the “platform version categories” (used to identify the platforms that are relevant for the article – e.g. Category:Windows Phone 7.5, Category:Nokia Asha Platform 1.0, etc) into the Article Metadata on the top right of every page.
This is more appropriate because the platform versions are more “flags” than grouping categories, and also means that the more useful “grouping” categories are now easier to see.
Platform version categories are still added in the same way (when editing a wiki article, select them from the category selector), and all categories that are known to be true for the article should be added.
Hope you find this improvement to the navigation and usability of the wiki helpful!