I really see Twitter as just a multi-user text messaging service. I don't follow a sh*t ton of people but it's another way to "hear" about stuff I am interested in. And I kinda like it.
Granted I don't play those silly FaceSpace MyBook games, so I'm not as wired-in as most. Considering that I work in IT and, thus, spend the majority of my day in front of computers, the previous sentence may seem counterintuitive. The other "Social Networks" [Christ, did I mention I hate that term] take significantly more of my time.