For me, it's a microblog. It's not a chat (it's a push medium, not a conversation) and it's not a blog (I take care and time over blog posts and only post stuff that I think is of general, lasting interest). Twitter is for quick stuff that's possibly of interest in the moment. Funny links, new music I've just found, whatever.

Yeah, I tend to follow those who say funny or interesting things, and I try to say funny or interesting things. I find I get some news faster than through other means, as well as getting the occasional laugh, or some insights into how other more seasoned developers do stuff.

and I'm at http://twitter.com/majicDave

No Twitter here... but the folks on TWiT (This Week in Tech podcast) all seem in love with it, and there seems to be quite a community in place. Maybe I should join so I can fit in with the cool kids of the internet?
Facebook is good enough for me... I must be an old fart...

Meh, I think it's just a hyped-up away message, but that's just me.