TechCrunch falsely reported that Google is testing a new ad format for email subscriptions - it is not new. Search for [crate and barrel] or other terms and you may see it come up.
The deal is, this is something Google has tested for two years now and made official a few months ago.
In any event, have any of you tried it? Is it something you recommend other advertisers give a try?
Forum discussion at WebmasterWorld.