I've been using Adesense since it was new. At first my CPM was through the roof, but as my traffic has increased, my CPM has crashed. I'm thinking about trying out some other programs and seeing if I get better results.
I applied for Yahoo's program. Maybe they'll respond to me sometime this decade.
Are there any other big ones? I'm looking for simple text based contextual ads.
I'm wondering if the quality of the ads you get might be related to the number of impressions? If I do a little PHP and rotate my ads randomly, I might make more total from all the programs combined than I would from any one program by itself. And it will be pretty easy to tell if I'm way off :-)