I often wish that Overture was more like Adwords so that I could increase my paid exposure. I find the down sides of Overture are the lack of imediacy. You have to comitt to a certain spend and wait days for keywords to be approved, so the sort of experimentation that is possible with Adwords is out of the question.
Strangely enough though, Overture improves my Google ranking. I have bid on several keywords for my
Book Review Site. Theses are returned as sponsored results in search feeds that other people use to pad out various pages. The end result is lot of links to my site at Google from various directory type pages.