In the last couple of days, I am noticing that if I do a search and arrive at my site the ad that shows up looks pretty relevant. But then I click on a second page and it the same ad. Click another page, same ad. This goes on and on and on. I'd say the same ad is showing for the first 5-6 impressions. How does this make sense for the user or me the publisher? It's like ads are not rotating evenly.
Running a quick report for the past few months on my main site shows that while CPCs for interest vs contextual are very similar, CTR for interest based ads are slightly higher. This explains the reasoning for interest based ads. Note that my site targets every country in the world however, so your results may differ.