Though it appears to be available on some boards and not others, versus only certain users having access to the new design, Pinterest looks to be updating user boards with tag-based navigation, similar to the “Guided Search” function recently rolled out on mobile.
In the first screenshot below, taken from my Automobiles / Motorcycles board, you can see that they’ve added several related tags, each of which links to a search results page for that topic. While this is great for content discovery, I would like to see users given the option of searching those tags within the actual board and perhaps some insight as to how and why those tags were suggested.
Update: It appears Pinterest has removed this feature for the time being. (5/12/2014)