There is a nice poll running at DigitalPoint Forums that asks AdSense publishers to vote on if they use Google Adsense's section targeting or not.
I explained section targeting in the past, and there is also this AdSense help page now that explains it a bit better. But in short, AdSense allows you to specify the content you prefer AdSense use within your page's content, to target for matching the ad relevancy of the AdSense ads to. It should help drive more targeted and relevant ads, which should help increase CTR and revenue.
The poll asks if this really works for you. Currently there are only 17 results, I would love to see more, since the results are pretty even across the board.
Please visit the DigitalPoint Forums thread at take the poll.