Thanks for this very useful plugin.
I have the following bug to report.
It converted the post type as intended. That part worked great.
However, I notice that when I view the Posts > Categories, WP will continue to show that there are posts inside the categories I have converted to another post type.
Let's say I converted all posts in the category "Meals" over to a new type called "Recipes", and I had 10 recipes in total. All 10 change from Posts to Recipes, but I will still see "10" as the number of posts in the "Meals" Posts category. If I click the "10" it will take me to the "Meals" category, and show that it is empty.
This leaves me to believe that perhaps the plugin is not changing everything it needs to in the database.