Overture seems to have created a whole search engine that is based exclusively on PPC results. Not sure how many people actually use the engine compared to the number of advertisers who pay for listings, though! But that's some food for thought. I think it's important to consider that the site visitor knows that the listings are paid for, and therefore might be skeptical of the results thinking they're not necessarily seeing the best guy, just the guy with the most cash.

It has been hit and miss in my experience. Remember that any PPC campaign can be looked at as a lead generation exercise because your doing just that. With Overture, GoogleAdWords and Espotting at least you know your dealing with reputable companies which very important on the net