My overall experience with them has been pretty good. I signed up after they started appearing at #1 and #2 in the Google results for some of my keywords/phrases.
Here are a few pros and cons based on my experience over the past month.
1. You only pay for clickthrus. (like Overture and Adwords)
2. Fairly low CPC's. Generally 30% less than Overture and 20% less than Adwords. Even at position number one.
3. Very responsive and helpful staff.
1. Manual bidding process and set up. They don't offer near the amount of overall control as Overture and Adwords.
2. Traffic is well below their estimates. Which is ok since it is a PPC program.
3. Traffic isn't quite as targeted as Over' or Adwords.
It does take some time to get the listings up and running but in my case it has been worth it.