I've spent 24 hours for migration my official blog from MangoBlog to BlogCFC. I don't want to clarify why I decided to move from MangoBlog to BlogCFC because most of facts have been clarified by Nil at his blog. http://nil.checksite.co.uk
For me, the important reason that I choose BlogCFC because of Mobile version and others are such as tweetbacks and gravatars picture from comment (which I really like this one :)).
MangoBlog has also advantages such as one-click-plugin-installation and themes which are based on Blogger and Wordpress. Please don't get me wrong either.
Database migration? No idea. I configured two databases by myself(manual) because my hosting is based on Railo which doesn't currently support ORM.