In addition to the old functionality, you now have the ability to choose a specific value among the known values for a given URL parameter. This is important when a parameter is relevant to the content, but different values of this parameter lead to similar pages. For example, consider a sorting parameter, like "sort-by" in the following URLs:
I find this to be a thoughtful addition to the box of tricks offered in Webmaster Tools. Faceted navigation can quickly pile up a mass of URLs and a site can still want at least one of the parameter values to be crawled - but not all.
Up to now, it was a tricky situation. At least this gives you a fighting chance to re-allocate some of those spidering cycles.