A lot of moms are apprehensive about changing blog hosts. I've successfully switched from Blogger to Wordpress and found it to be very easy. Have you changed blog hosts before? How was your experience?
In a perfect world I wish all of my blogs were run off one platform and one host! I use Movable Type for Boston Mamas (my primary blog) and I love the amount of control you have over layout and such. However, to use the free version it's a bit of a bear to install so you either need a tech friend, or go with a hosting company that offers install and tech support (such as Pair.com, which is what I transferred to after nasty GoDaddy pulled the plug on my site without warning).
My Posh Peacock design blog is run on Blogger and my personal blog (Pop Discourse) on Wordpress. Both of these platforms are super easy to get started on but I would recommend Wordpress over Blogger to novices since there isn't an easy way to backup on Blogger (as there is on Wordpress). Eventually I'd like to move my Posh blog over to Wordpress for simplicity; I just haven't gone around to it yet.
Anyhow, I'm not quite answering the query above, but hope this offers some insight into 3 different platforms!
Yes, from TypePad to WordPress. I had a blog for ClubMom and when they laid off their bloggers, we were able to take our content with us. I already had TypePad blogs and wanted to try self-hosted WordPress and worked with a techie person to do that, so it was easy. Unfortunately, the pictures didn't transfer over, so I had to go in and redo all the posts and add SEO keywords to them as well. I still don't have it all done and it's been over a year. It takes a long, long time.