I just can't say how much my website needs this. In another thread, I was complaining about poorly targeted Yahoo ads. Ask and you shall receive. YPN now lets you choose which category of ads to show on your web page. And... it works fast! Now, if only Google's Adsense had something like this.
Are you seeing good selection? I just got set up, and tried this out, and while I could see a change in ad inventory quickly, I was still a bit disappointed in the selection.
The selection is better than it was, but still not great. The categories you select from are too broad to really target a web page properly. But, I guess, one step at a time.