For bloggers (publishers) the ad units are called Google Referrals and on The Digital Napkin you will find them on the right sidebar, just under my subscription links. Feel free to click on them and and look around the advertisers site because they are no longer paying Google (and me) for the click, instead they are paying for a completed transaction (of course if you you do like what you see make sure to purchase something). In effect, they are removing any chance of click fraud.
This helps the advertiser control their ad spend, by tying a dollar amount to an action, (subscriptions, purchases, etc.) and it helps the publisher by paying a higher dollar amount for the referral. In essence, Google has created an affiliate network.
I wouldn't suggest that publishers get rid of their PPC (pay per click) adSense ads completely but this allows them to diversify their advertising inventory and should be a win-win for everyone involved.
This also represents an excellent opportunity for online sellers to manage their Google advertising dollars, by tying the advertising amount to a completed result. For example, let's say an eBay seller is currently paying eBay $2.50 for a completed sale, that amount can vary depending on conversion rates for that item. With Google PPA, a seller can sell that same item on their website and say they will pay $1.75 for a sale of that same item, give the customer a 25 cent discount on the sale and still make 50 cents more for the sale than on eBay. For media sellers, this is a savior because they can now afford to advertise with Google and draw traffic to their own website. Had this program been available in 2005 when Glacier Bay was trying to convert to web sales, I would have chosen to stay in business.
I'm really looking forward to this as a publisher and if I was still a seller I would be all over this.