For me at least it would be nice if there was an option to have sub-catagories under sub-catagores. For example:
GM (Parent)
Chevrolet (sub)
Chevelle (sub/sub)
Corvette (sub/sub)
Nova (sub/sub)
etc....
It would also be nice to be able to put items in the parent, for me I have parts that fit several several different models and it would be nice to catagorize as such.