I use WordPress.com. I like it because I think it is easy to use and looks and feels more professional than Blogger. My biggest complaint about WordPress.com is that I can't use Javascript on my blog.
I liked Blogger because it was really easy to customize and I could make it look exactly the way I wanted - the code was probably a mess, but I didn't care. There were a lot of plug-ins/add-ons for Blogger, too. I got more detailed traffic statistics using an add-on.
I switched for two reasons. First, I wanted to be able to post under a password sometimes. Second, when Google scooped up Blogger, it made it nearly impossible for me to be logged into Blogger AND to my personal (non-blog) Gmail account at the same time.
I never bothered with Typepad because it wasn't free. This may not be true now, but when I looked at it, even after you'd paid you had to have ".typepad" in your URL. If I'm paying, I want the ".SERVICE" part to go away.
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