Quigo has been around for some time. Offering various products, they have stayed in the mix when many others have folded their tents.
They have been offering their AdSonar product for over a year now - though CNNMoney in their article today makes it sound like they are something new. I don't know if I would call them the "next Google" as the title of the article suggests, but I am going to test the claims and see how it does for a small amount of our traffic - say a couple of hundred page views for a month.
It would be nice to have an alternative. And the one thing I like about their product is the advertisers get to bid individually on each publishers available inventory. So the good ones will get more and promote sites to strive to be better to gain more income.
Then the arbitrage game would be about improving your site as opposed to just throwing it up and starting another one.