I am on it and I LOVE it. I communicate with my daughter and friends on there, and I follow a wide variety of people. Most of the people who have asked to follow me are friends, and some follow me because I have similar interests to them. I can block anyone I don't want following me.
I actually joined because of a woman I saw on Good Morning America. She said that a lot of people are finding jobs through people they talk to on Twitter and Facebook. I started following her, and I sent her a message asking about legitimate online jobs that you can do from home. She sent me a couple sites, and I joined them.
There are definitely a lot of weird people on there, but I mostly keep it on my home page, so I only see the people I follow. My husband has found lots of people involved in CAD, which is the kind of job he is looking for.
I love how instant it is. In fact, I read that when Lance Armstrong (cyclist) had his bad accident last month, he sent a message to Twitter about it, and the world knew about it before he got to the hospital and the news media found out about it. A lot of celebrities like it because they can squelch some rumors before they have a chance to spread.