if I have my smartpen why I have to use a Digimemo ?

I just saw this SolidTek DM-L2 DigiMemo L2 8-1/2-by-11-Inch Digital Notepad demo video. Very nice review but it has raised some doubt in my mind. If I can use my smartpen (no matter what iogear type or livescribe type),  why I have to need that Digimemo ? Ok It has a text to type software converter which is seems very convenience, you can convert your writing paper into a pdf format, and you can send email by using this device. but almost of every smartpen can do that, isn’t it ?

Could anyone who using this Digimemo help me about this, I would like to know why you using it ?