I have been doing some experiments with ad unit sizes and placements, and have been able to improve my adsense ctr quite a lot. The full description can be read at increase adsense ctr
This is one of the method to increase the impression, the thread starter seems doesnt know that to earn more from adsense, the "clicks" are needed
Thanks for posting your findings. I also have experienced that square ad units convert the best. (at least from what i have seen) While its good to have multiple ad units, I have heard that it can decrease the CPC if your page maxes out with 3 ad units.