Jesse Ruderman has a great post on Switching from Movable Type to WordPress for those contemplating the switch. The article goes through some of the advantages and disadvantages of WordPress over Moveable type and talks you through some of the problems encountered in the move (along with some solutions and fixes). Very worthwhile post for those tweaking and upgrading the back end of your blog.
Switching from Movable Type to WordPress
Problogger.net runs on the Genesis Framework
The Genesis Framework empowers you to quickly and easily build incredible websites with WordPress. Genesis provides the secure and search-engine-optimized foundation that takes WordPress to places you never thought it could go.