Typo needs to work on their migrations...
I use Typo, because I like Rails, and it's free, and the feature set is pretty nice. But often I find that migrating between major versions sucks.
I just upgraded to 6 from 5, and experienced a problem every time I tried to read an article imported from 5. The failures looked something like:
ActionView::MissingTemplate (Missing template /articles with {:handlers=>[:erb, :rjs, :builder, :rhtml, :rxml], :formats=>[:html], :locale=>[:en, :en]} in view paths "/blog/themes/scribbish/views", ...)
After digging around a bit I found the culprit.
New Typo apparently supports multiple presentations for content, and now has a 'post_type' column in the contents table. If you write a new article in Typo 6, it will get the value 'read'. I went to my database and updated all the old contents to have post_type of read. e.g.
UPDATE contents SET post_type='read' WHERE post_type IS NULL;
After this, all my blog posts worked.