"Some of my sites were up 30% while others were down 20%. My content is all original and really strong. Not a content farm. I run ad-sense on some but not the others." - This type of post is worthless and clutters the forum. If I had one wish for WebmasterWorld for the coming year it would be for forum members to self police their posts by asking themselves "Is my post adding to the conversation or not?". "Reporting" how an update impacted you akin to saying "it snowed at my house too" after a blizzard. Really? Wow... thanks for the insight.
My thoughts on the update: Google identified the large content syndication sites and devalued them along with sites linking to and from them. The Sistrix report (can I mention this on WBW?) shows a substantial list of these sites and their estimated traffic losses. My initial hypothesis is that Google identified variables associated with "content farms" -high publishing volume, poor inbound link profile- and devalued them along with sites that link to/from them. IMO, if eHow (again, hoping I can name them) indeed avoided a decline it is because eHow's back link profile is slightly better than the restof the "content farms".
This is all just my hypothesis. Hoping others can chime in with more thoughts on what Google changed then how it impacted their particular situation.