There are some I like to read when they get linked. I dont' really have any streamlined way to view them, though. Some of my friends keep them, so I like to support their blogging habits.

Tumblr is a completely different sort of beast from the existing blogging sites. It's a lot more... crowd and sharing based. I hesitate to say "there's little original content" because there is, but the focus is definitely on linking and sharing things you like. I kinda like that, and if I were to restart my What I Learned Today blog, it would probably be suited to Tumblr.