I'm not into Death Note myself, but I know enough about it to participate in this thread.
I wouldn't kill anyone. I wouldn't try it out. Why? Because I'm not a bloodthirsty maniac.
I would then burn the notebook so nobody else could it instead. If it turned out to be impervious to flame, then I'd bury it deep and hope no one would find it.
Killing bad people makes you just as bad as the people you're trying to "purge."