My Thoughts on Blogs
I will agree with the first point. Almost all blogs are run by political activists giving their opinions, and most of the readership is from that group of people. This is partially because blogs have become so streamlined with their thinking. Originally, people did blogs b/c they could be anonymous and give their true feeling of a situation at hand. Now, very few bloggers are truly anonymous and therefore cannot necessarily give their opinion without sounding like they are bashing their party. For example, I did not see one single blog that thought the governor's race would be won by the opposite party. Why? B/c most bloggers are political activists within their parties and want to be viewed as team players. Going against the grain would only hinder their ability to make a difference in their party.
On the second note, I am in less agreement. Every site has an agenda, the key is knowing what that agenda is. Not Larry Sabato's Ben Tribbett is well known for disliking Dave Marsden and Gerry Connolly. Even so, readers know this and take his commentary on those issues with a grain of salt. Same goes for Too Conservative's Vince Thoms opinions of Sean Connaughton, Tom Davis and Jeff Frederick; as well as Republitarian's opinion of Matt Lohr and Mark Obenshain. If you want to read these blogs because you agree or disagree with them, fine. At least you know where they stand and why they have an iron in the fire (for example Ben Tribbett ran against Dave Marsden, or Republitarian supporting Matt Tedrick). This is no different than Shaun Kenney writing about tax increases or "RINOs" (after all, Kenney was a VCAP challenger). We know where he stands as well. Any of these blogs are good and bring useful information to the table, they just have to be viewed through the prism of their own personal biases toward certain individuals as well as their political ideology in general.
I think blogs can be a useful tool for activists to use to gauge what others think about the candidates and/or issues, but I doubt they will ever become a "mainstream media outlet" that a vast majority of the public uses to determine their votes upon.