I've also signed on with Twitter. I have to say, Twitter ranks high on the list of things I didn't see any appeal to until I tried it. It always sounded so inane— "Having hot dogs for lunch," "just put bills in the mail," "So happy it's Friday." And some folks do use it for that. But the Twitter experience depends on whom you follow.
If you're not familiar with Twitter, once you have an account, you can look at the "public stream" (gazllions of posts from every single tweeter who doesn't protect his/her updates) or you can see only posts from folks you select, or "follow" in Twitter-speak. Finding them is easy because you can search for names or keywords using the Find People menu. And once you find someone to follow, you can look at his/her list of people they follow.
People with a public persona often use Twitter to market themselves. This includes authors, agents, editors, marketing consultants, celebrities, actors, ad infinitum. If you have an area of interest(s) (for me, it's spec fic, book publishing, and ebooks), you can create a list of tweeters in that area, and then sit back and listen in as they chat about what they're doing, what they're selling, or just what they're interested in. If you follow enough people (I'm up to about 500), you can click the Home link every 30 seconds and see new posts.
At he same time, once you send a few tweets, people will start following you (Twitter sends you an email). Some folks you follow will follow you back. Twitter has gotten so popular that there are now Twitter-specific software apps that let you organize your following list and send tweets to multiple places. Some folks follow tons of tweeters, hoping they will return the compliment. I actually consider carefully before following back. Some of these people are selling porn, for one thing (Twitter lets me block them), and some are just marketing themselves and I'm not interested. One person has followed and unfollowed me ten times. I assume he's using an automated program because otherwise he'd recognize my name just like I recognize his.
In thinking about it, there are three reasons I like Twitter. One is, unlike Facebook, I can follow anyone who hasn't protected his updates, which means I can keep up with authors I admire, like Neil Gaiman, an active tweeter. Second, I see news on Twitter faster than anywhere else. And third, it's just plain fun!