Look at other options first
The best thing about this package is the pen. It's sharp and accurate. In fact the sharpness of the pen demands that your DS should have a protective film on it, or else your screen would easily scratch with this one.
But the sharpness also brings in a level of accuracy that you may never be able to achieve with the default stylus.
The pen is definitely the biggest reason to buy this pack. Everything else is just a bonus (though the extra stylus sure does serve as a good backup).