Larry,
Haven't tried overture, but tried google.
Now, google is the best in PPC buisness AFAIK. They offer high pay . But you have to really carefull while using google ads.
There were also horror stories of google turning them down at the end of a month when the pay should be delivered. They wont allow any other ads to be displayed along with adsense, if they do find, they will disable the account and will never respond to any of the mails.
. The ads delivered by google are amazing...those content targetted!!
Clicksor is one such PPC, but it doesnt offer a high pay as google does.Adhearus is also a good PPC. Google is the best in buisness, but have to play safe .!