I've heard rumors of this coming for awhile, but I finally saw it while browsing DaniWeb just a couple of minutes ago. A box ad that I run with a white background, which usually displays four ads, now displays three. The extra room is reserved for some text links with a bunch of keywords, similar to the link units. However, instead of opening a new window, clicking on one of the keywords dynamically refreshes the IFRAME to present the user with new ads, in addition to making room for a search field built into part of the ad box (Many of you have noticed this when it displays in a link unit when no relevant ads are available).
I definitely like the idea. It combines the advantages of the link unit (seeing the keywords Google picks out for each page, and allowing the user a greater selection of targeted ads) without the huge disadvantage of requiring not one, but two clicks, in order to generate any revenue - not to mention that the second click must be made after the user has already left your site.
While logging into the AdSense Reports didn't come up with any new options, it did explan why I was pleasantly surprised to find a noticably improved CTR today.