Google's Matt Cutts announced today on Twitter that Penguin 2.0 rolled out today. Matt Cutts Tweet:
This update is expected to affect about 2.3% of English-US queries. This is really huge. In fact as I look across multiple search results, I notice that many different search queries results barely resemble what they did yesterday. The update is supposed to improve the quality of results, but I see many results are far poorer than before. Let's hope that Google makes a further change to improve these results.