I've uploaded photos of various Google AdSense test units before - but I've been seeing this new AdSense unit quite regularly and really like it.

The arrows scroll through other relevant AdSense ads. The interaction is immediate and slick. And I anecdotally, I've found myself rolling through ads out of curiosity or interest (hoping to find more relevant ads). My guess is that the data Google is able to capture from user interactions / clicks here is potentially more powerful than their AdWords data. Fascinating stuff.