I do see a lot of dance in search engine positions of a few sites I own and a few clients sites. Interestingly, some have gone drastically, some have shot up quite a lot too. Not sure what's going on, but I'm doing a lot of testing now for the past few days; should have some direction soon about this. I guess instead of just posting your experiences, sharing some observations might help in identifying what could be the cause of this "penguin" attack.
One of my quick observations is that there are no sitewide penalties. Specific keywords have gone down. I own a private network of blogs and the network is intact, so there's no deindexing happening.
Any other inputs?