Adwords have released the long awaited placement performance report and also created the corresponding help center entry. I cannot see this in my account yet but hopefully it will be available to all advertisers soon.
I am using it and I really like it! The new report is giving me the opportunity to really test some different keyword grouping strategies, bid and positioning strategies, etc.
My personal ads are all image ads through the content network. I've had some issues with non-relevant sites but the great thing about the report is that it makes it super simple for me to exclude those sites now.
I pulled a report for a client who uses text ads on the content network and I was really impressed with the relevancy for the distribution for his ads. Relevancy was much better for his than mine but we have two totally different industries and ad formats.