Well, imagine my surprise when I discovered that a bunch of my old entries no longer worked right in Typo? The problem is, out of the box, Typo doesn’t bother showing the extended portions of entries, even though it does store them. So I sat down and started poking around the internals of Typo and got it to not only show the extended part, but also to let me edit the extended part from the admin interface. And it didn’t take very long at all, because of how powerful and flexible Ruby on Rails is.
And then, after that, I read up on mod_rewrite and added rewrite rules to get all the old MT URLs to point to the right place. Hopefully I didn’t miss anything.