There's definitely something going on! I saw a drop of 4 positions in one of my (very few) niches, and a 10+ drop on the others, but all the sites are recent.
In the niche I dropped 4 positions, my site is the only site on the top 10. Google's first page is now dominated by two forums and the rest is FB pages. And most of those new "neighbors" weren't near first page before! Let's see how things stabilize in the next couple of days, from what I read this things take time. It's my first penguin, so I can't compare its strength to the previous ones.