It's not verry interesting, I mean that if you know how to edit NBT data files, you can do it, and much more (Have you seen the singing sword ? Well I made it! Using &k !)
We (l33t mapmakers) all know how to edit NBT data thanks to SethBling, as well as our creative minds, and some other jazz. Dinnerbone was hoping to allow us to do it in game thru use of commands.
If you didn't think of adding commands to edit NBT data in-game within the first second of learning about NBT data, you're not very creative. These kind of ideas should click very quickly in your head, whenever you do anything.