I've been showing a bottom anchor ad on my sites for several years, and it's always been OK but not great.
I recently signed up with Infolinks, who specializes in showing the anchor ad with what I think are ads they sell, not just glorified Adsense. They guarantee a 100% fill rate and a guaranteed CPM.
It's only been a week, but so far the money I've made from the anchor ad from Infolinks is about 6 times what the anchor ad was making before!
It's really making about as much as all of my other ads combined :-O
For those of you struggling with Adsense revenue, so far I think that this is well worth checking out!