In my opinion, using categories is a useless tasks that just requires more manipulations.
In most cases, if an item is on a NA list, it is not important whether it is a personal or business or wathever item.
If I look to my @Calls list, I want to see all the calls I want to make, because maybe I have some time to do a personal call.
Don't overcomplicate your system, it will only lead to giving it all up. The best systems are the simplest ones.