I mentioned in November that Google tested an OneBox at the bottom of the search results that lists recent blog posts related to your query. Now the OneBox is live and can be triggered by adding "blog" at the end of your query (for example: search for search blog, music blog, google blog and look at the bottom of the page). You'll also find it for other queries that contain "blog", like Google Groups, as there are a lot of people who talk about the new version of Google Groups.
As Google Blog Search updates much faster than the general index, these results can be found only using a blog search engine. At least for now. Then they'll become a part of Google's main index.
Google offers a lot of OneBox flavors, that enhance the search results by adding results from specialized databases or by providing a direct answer to your query.
1. Do you pay attention to OneBox results?
2. If you can't find a good result for your query, do you try specialized search engines (blog search, Google Books etc.)?