One of the biggest problems I find is that I want to allow users to add categories using freeform as well as select from a dropdown of current categories. As well I want to allow users to add sub-categories. Freeform is great for making categories on the fly but there is no user friendly way for the combined approach.

E.g. I want create a page about jet planes. So create content>page, pick the 'planes' category and type in 'jet planes', enter my content and save. Now when I return to create another jet plate page I see the category right there.

In my oppinion this feature alone would push the category module past taxonomy and right into the core.

If I am missing something and there is an easy way to do this them please let me know.