Who knew? I just took a blog that had been languishing under MovableType 4.01 and migrated it over to the shiny new WordPress 2.6.3
The MovableType export format is still importable into WordPress with little trouble. I wrote a MovableType template to export all blog post titles and URLs so I could craft a .htaccess file to preserve old URLs, and that took a few minutes to work through reformatting from a plain dump to usable .htaccess structure with Redirect 301 directives. But not difficult, with the help of TextMate and regular expressions :-)
The hardest part - by far - of the process was figuring out file locations, permissions, etc... on the target server. The migration was trivial once I worked that out.
Here's the MT Template I used to generate the text that got processed into the .htaccess file for wordpress. There's probably a better way, but this worked for me.