I summarized the reasons in this post: Why I Switched From TypePad.com.
Now it’s time to update that post with the following, from TechCrunch: WordPress Boosts Free Storage to 3GB. Leaves Blogger, TypePad in the Dust.
I encourage anyone just starting a blog to seriously consider WordPress.com. Not only is it better than TypePad, but it’s free. And I encourage anyone who has a blog at TypePad to stop wasting your money and dump that POS.