Twitter is eating me up. I start my work day just fine, but then I got distracted by an article on Twitter in Time Magazine, and an hour later woke up from Twitter plunging.
If you're still scratching your head about how to use it, or if you should use it or not, here's a series of articles from Time that will help you decide:
Let's put it this way: you can waste time with Twitter, or not. It can be a BIG source of traffic back to your blog or website, if you use it properly. At the minimum, you should set it up so your blog updates are automatically fed into your Twitter updates. Use TwitterFeed.com for this.
If you're a small business looking to sell products and services to other businesses, you need to start using Twitter. I don't know about other social networking sites. Well, I do know about them (Facebook, LinkedIn, etc.) but I'm just not spending time on those like I do on Twitter.