We've been happily using the free Google Ad Manager on Kongregate for 18 months or so. We're way higher than the 90M monthly impression level so it looks like we'll have to start paying. I don't mind that if the terms are reasonable and they keep improving it...
I'm amazed this is not on the front page (as of this comment, anyway). I haven't had time to fully process the announcement, but anything Google does in the advertising space is going to have a fairly big impact.