It really depends on how you use it. It's good for blasting out short thoughts, links to articles or announcements to a large number of people (I have about 1500 followers), and those various "tweets" from different people can be organized by topic with the hashtag. Then people can respond with their own thoughts. One nice thing is since you aren't posting anything beyond those 140-character tweets (as opposed to a bunch of personal info) you don't have to be hesitant to connect with people you don't know in real life, unlike on Facebook. Some people also coordinate their tweets with their Facebook status messages so that they reach even more people. Twitter is one of the few places on the Internet where conservatives are ahead.
My personal advice: if you're still getting comfortable with Facebook and MySpace you don't need to be in any hurry to get on Twitter. It will still be there when you're ready!