I have only had Adsense on a site for about 4 days and the results are excellent so far. However I find it hard to figure out how they are so good as about 80% of the time I am seeing charity ads.
However I am in based in Ireland. The bulk of the site users are UK or USA based. Are users seeing ads that I am not because of the likelihood that many of the advertisers are not adding Ireland to their countries list?
It seems the answer is likely yes, which is a bit disconcerting as it means I have no real idea what ads are being run at the site.
I had a friend in the USA check it for me and she sees ads I have never seen, so it would seem the answer is that they are served in accordance with the regional settings.
She saw some that had I known they were there I would have blocked, but I won't for now anyway, they are earning too much to do so and their presence does not seem to have affected sales from our site at all.
As an adwords advertiser, the FAQ and set up suggests very strongly that all ads are regionally targeted if you use that filter, no matter whether google search, partners, or adsense sites. If Adsense ads were not, Google would have to make some very quick changes to their Adwords interface and FAQ's!