RhinoFish - 4:13 pm on Dec 5, 2012 (gmt 0)
If the PPC is built well, the CO is wonderful. If your PPC isn't good, it's like putting cruise control on a car with a flat tire that's firing on 3 cylinders.
The CO frees an enormous amount of time regarding keyword level bidding, and, in addition, the efficiencies of that bidding for results automation FAR outweigh your techniques. Yes, returns and adjustments are an issue for the feedback loop, but they are so minor compared to the gains it's silly.
Caveat: many disagree with me, and say the CO doesn't work for them. I assert the underlying PPC has issues, but there can also be business issues I suppose, like a high return rate, that also makes the CO less optimal. The CO needs time to "learn", suggest you try it on one campaign, see what comes, for you.