I love it. I didnt get it for the longest time, but like most social media, it's value is in the people on it. Sometimes you just hear about what people are up to, sometimes you get poignant thoughts, and other times it spirals into full-blown conversation.
The limited space (140 characters) forces you to be concise, and ensures you're never overwhelmed.
I follow friends, of course, but there are some others that are worth checking out - particularly rawkhawk, which does excellent record reviews in (140 characters!), CNN, which is judiciously updated, and, of course, THE ACTUAL cobra commander.
The real reason for this post is tweetwheel. It's a cool visualization of how those you follow on twitter are connected. You can check out my tweetwheel, or see your own.