i have it on many of my sites, but theres no results. i have it set to only search my sites, but it seems as if the pages have to be indexed on google to be in the results. if thats the case the adsense for search does me almost no good, until my site is page rank 4 and all my pages are indexed.
You don't need a PR4 to have all your pages indexed. Do your sites have original content? How long have they been up? How many incoming links do the sites have?