@weaselmeyer - AdMob does not let you target particular markets like Google goes when it comes to showing ad. For instance, my app is wine related but there is no way to only show the ad to wine drinkers. This is the biggest weakness in my opinion.
In general, I want to like AdMob but with my testing I have not found any + effects. Here is an article I wrote on a test I did with my own app:
Results from my Great Advertising Experiment | How to Make iPhone Apps
bottom line: no effect. I did not loss tons of money but I also did not recoup.
