Does anyone use this service to promote your comics, if you have your own site that is. I'm curious about how effective this program is. Any insight would be appreciated.

I did a test campaign for this, and unless you want to make some large bids it's just hard to get anything out of it. Adwords is really more geared towards businesses that want to convert a click into a large sale, and thus will pay multiple dollars for their CPC.

In my experiment I used my target CPC at Project Wonderful ($0.05) for a few months, and got about two or three hits over that time. Now, I really didn't try to tweak my keywords beyond a decent starter list, but in comparison to the traffic you can get out of PW for the same CPC it's just hard to justify the time investment in fooling with it.

Just as an added note, Google traffic tends to be much more generic in what they're looking for, whereas PW traffic tends to already be in a "comic reading" mode. Of all the traffic sources I use, PW has the highest percentage of users who read several or more strips on their first visit, and as a result the highest percentage of returning visitors.