When I decided it was time to make a blog, I knew I didn't want something that looked like every other blog out there. I wanted a lot of control and flexbility, because I read that some folks (like Natalie Jost) have found that a "turn-key" blogging system can become frustrating because it gets in your way when you have creative ideas about how you want your site to look and work. I bet I would feel the same, and although I'm no designer, I am a programmer so I wanted something built with a modern framework so I could hack on it and add new features. I love Python so I picked Django, and so far I've found it easy and fun. As Jeff Croft writes, Django comes with some nice built-in functionality for blog-like sites.
So far, I've got a captcha for preventing comment spam, and Ecto integration via MetaWeblog. Picking a blog API was a tough choice, and I looked at Atom too of course. But even though MetaWeblog has problems, it seems to let Ecto support images better than Atom does. Anyway, I'm looking forward to doing some social bookmarking integration, i18n, photoblogging, and lots of other nifty things like that.