We've had a lot of experience with Admob, and also with Mobclix. I'd recommend the latter.

For some types of applications (such as news readers, definitely not action games), ads can work very nicely.

You can expect something a eCPM of $1.20. In our case, that translates to like 6 cents per click (which is a metric I like more).

We have a very shallow comparative in our blog: http://www.androidsx.com/admob-vs-mobclix-1st-round/