Best way to migrate your blog?

With the release of the new beta blogger.com, I wonder--what happens after years of blogging one blog system and finding that one wants to migrate to the latest and greatest on another service; or maybe your blog system gets blocked by the largest democracy in the world? Say today, blogger wasn't releasing an updated site, and I wanted to take advantage of a more powerful blog like typepad. Granted, I have under a year of posts under my belt, but keeping even the little history I have is important. It is plenty lockin to keep me from entertaining the thought of moving systems--unless there is an automated service that would make it a completely seamless transition. A little google sleuthing turns up WordPress migration from Blogger or Typad, but I cannot find any other resources. Maybe this is just an obscure thought--but my hunch is that among the 50M blogs out there, many would want the freedom to migrate to the best product at their desire. Well--I suppose my aspirations for migrating to TypePad will have to wait--and hopefully I'll get into the Blogger beta soon... as tags and a little AJAX will be nice to have.