i had great relevancy. of course, i dont use ad targetting, so my ads are contexually targetted. now, however, i am finding 1 ad block highly targetted and the others struggling to fill the ad space. personally, i liked having duplicate ad units. i am restructuring my ad layouts now to remove these extra irrelevant ad units. it might negatively effect my revenue, but i dont want my visitors clicking irrelevant ads... that only leads to the whole "low quality traffic / poor conversions" story.