I've been with them for many, many years and the past three months have been a roller coaster. I have already begun replacing some of their ad spots for affiliates and I am getting close to flicking the switch on the rest of the site, as well. It's just a difficult decision, as I've had a lot of success with Adsense over the years.
I've found that Adsense works best with directory and rapid information websites. Amazon seems to work better in informationally sticky websites where users are more interested in reading content than quickly searching for information. That said, yesterday was abysmal but it may have been due to the five day outage caused by a service provider "upgrade" that managed to lose a /24.