However, Google Blog Search doesn't work as you'd expect. If a topic is in the MSM, Google Blog Search often finds the MSM sites first. If a topic is only in amateur blogs, regular Google is a better way to find where it's being discussed.
One reason for the problems with Google Blog Search may be that there are ways to improve your indexing in it, and web site professionals are more likely to use them than regular bloggers. For example, see the Google Blog Search Pinging API and the simpler Ping-o-Matic. This gives an edge to the commercial sites. Commercial sites are also probably more savvy about how to take advantage of Google Blog Search's search rules.
A little poking around makes me think that Google Blog Search is junk and should be avoided.
Here's my research...
First, I opened Google Blog Search and searched for "Conrad Black" ( a topic that is currently both in blogs and MSM). Of the first two pages of links (10 per page), none of the links were to amateur blogs. All of them were commercial operations with editors and staff. Some links were to "blogs" on big media outlets like the Wall Street Journal. Some were just to MSM sites with (in this case) no blog content, like Macleans and Canoe. There was also a really creepy online betting site.
I decided to try a topic that is in amateur blogs but not in the MSM, so searched on that great obsession of Canadian bloggers, Jason Cherniak. In this case, Google Blog Search seemed to work fine, and provided 270 links out of a total of 1,368 reported pages. But then I searched on "Jason Cherniak" in regular Google. This returned 200 links of a reported 62,900 pages... and I didn't find a single hit that wasn't a blog. Regular Google was more effective at finding blogs than Google Blog Search.
I tried searching "agblosticism", a term my friend Tom made up that has appeared in only three sites, all blogs. On Google Blog Search, only two sites were found. On Google, all three were returned. (The third site, Quick Study, is clearly a blog but apparently doesn't appear as one to Google Blog Search.)
Finally, I searched for my blog - first its name and then its URL. Again, Google Blog Search was a great disappointment compared to Google. It was even worse when I searched for a topic I have blogged on. For example, I have written a lot of stories about the environment, so I tried searching for "yappa ding ding" environment. Google returned over 500 hits; Google Blog Search returned one old post.