The CPC can be effective if you have the upfront money to get started with them. I personally didn't like it even though I did run one on google for 2 weeks and got 2 sales out.
Here is what I did to try it, I signed up and I am cheap so it was $20 a day max
Then the first couple of days I wasted money just learning the setup and figuring the best keywords. Then for 2 days I ran the highest amount per click it was like 3.50 per click still on $20 a day and it did get me to the top of the list and I did get 2 sales during those 2 days, then I got cheap again and cut it off. Then I let it run at $20 a day at about 50 cents a click and got nothing not even clicks so as you can see in order to be effective it can really add up. Hope this helps.