I've been using Adcenter with mediocre results. I use both the content and search networks. It's much easier with Adcenter then adwords, and you can have multiple accounts. Also, when they lower your quality score, they don't tell you, but you can contact them via live chat, and even phone to get it resolved.
They are strictly business. They want your money but they also want to deliver a good product to their searches. Adwords just wants everything their way, Period!
What kind of offers are you promoting on 7 searches? Not specifically just in general: Clickbank or CPA? I'm doing both with AdCenter.
Facebook PPC is nice because you can dial in your targets, but they tend to die off after awhile. When you have a search engine you are showing up for people who are constantly searching. New customers everyday. Facebook you are showing to the same pool, so they suffer from banner blindness after awhile, then your numbers drop. You should always be working on your next 2 facebook campaigns.
Hope that info helps or at least sparks more info from other people.
-Capp