martinibuster - 5:00 pm on Sep 23, 2011 (gmt 0)
I've been seeing this new layout off and on for a week. I PM'd Robert Charlton about it at the time but then it disappeared. Maybe they're testing to see how users interact with it.
Just like the OP, I also thought the cache had disappeared. The flyout preview thingy isn't intuitive nor obvious enough to know that it's there.