Cool. Cool.
Pros (including soon to come features):
You can message people on NG quickly and without the use of e-mail.
You can inform your fans of stuff without having to individually e-mail them all (which gets kinda sticky when you have several hundred).
Cons:
Flaming.
Making conspiracies easier (they'll plot to have me assassinated they will!!!).
Needed changes:
A warn button. If a user gets enough people who've warned him for harrassive messages, it brings it to the attention of a mod who will review their messaging history or just simply ban them.
The ability to read sent messages.
(I had more, but I can't remember them at the moment. Will post later.)
Now I just have to sit back and let my post go unread by anyone of signifance among dozens of this thread's pages.