I was going to chime in on these topics yesterday, but I’m easily distracted and forgot.
As someone who has recently moved domains, I know from first hand experience that Blogstreet is about as user unfriendly as can be. While they run an excellent service for RSS feeds, just try to adding a new blog. Argh!
Both Blogstreet and Myelin are biased towards blogs that have been stable for a long time. The Myelin crawls appear to be very old. If you want to see this in action just check each site for Wizbang.
Blogstreet For Wizbang
Ecosystem For Wizbang
Myelin (Not up to date – no references)
]]>< 
I actually e-mailed back and forth with Phil of Myelin last weekend. He’s in the process of a major upgrade but it’s apparently a very cumbersome process–and very slow.
I noticed he had a beta version of it up, but the crawls behind it aren’t complete yet. It looks good though. That’s always been my problem with Myelin – a friendly interface to the dataset.