Here's why, and I've been using it just for a day:
1. Layout customizations
2. Posting takes less than a second to complete
3. Blogger Image Upload is pretty cool
... why it's a bad idea:
1. If Blogger is down, your blog is unavailable to the World. But then again, the 95%+ uptime is good enough for my blog.
I am going to post a story about how to do MUI stuff in Windows tomorrow.