Sand - 12:57 pm on Nov 30, 2012 (gmt 0)
I noticed a nice lift on the 27th (on a pandalized site), so I'm surprised to hear this 21st date being confirmed.
As I think about it, it makes sense I guess. It could have rolled out on the 21st, but I didn't notice because Thanksgiving weekend is dead for my site. Monday may have also been a wash on account of Cyber Monday (people spending their internet time on sites other than mine).
So there's a good chance I wouldn't have noticed until the 27th anyway.