Thanks for providing this work. It was really helpful.
I used to have a heavenly customized them for my book publishing company where I had to used one category as a workaround for a special post type. I was to lazy and also a bit scared (never change a running system) to create special post types and bypass my old ones to them.
With you plugin and another one to switch only post of a certain category to a new custom post type I was able to do this all in a few seconds.