There are A LOT of people earning six figures a year and more with adsense. The ones who don't are the ones most likely to post - and it's surely not a get rich quick scheme. What does it take to try adsense? Probably less than 30 minutes to apply and put up code. If you don't have that much time to give it a try, then it certainly isn't for you. I'm surprised you have enough time to post about something you have never tried and apparently have no interest in trying.
It seems to me that Adsense throttles down your earnings per click if you start making too much money. I saw this with Sedo and Godaddy cash parking so maybe this is normal. As for customer support Adsense is the worst. It seems like an abuse of power to me. Anway, this all my opinion, everyone has theirs.