As is obvious from the screenshots above, the paid-for listings look exactly the same as the normal search results when you look for an app in the Play Store. The only thing that's different is that small "Ad" mention, in white text on a yellow background, which can be found immediately to the left of the developer's name for the sponsored app.
How well those ads will be tied to the actual search terms you've used remains to be seen, but Google certainly has a lot of experience here from web searches. So perhaps this new ad system has a chance of not being too annoying, and maybe it's even sometimes going to be useful.