I use it heavily and find value in it for these reasons:
As an IT professional, I have made an incredible amount of industry contacts and learned quite a bit through the connections I make. Example: I attended a fantastic information security conference in Albany, NY last month hosted by the State of New York. It was $150, yet the quality and caliber of similar conferences is usually in the thousands. I would never have known about it if I didn't use Twitter. Again, as an IT professional, many of these same contacts work for the largest IT vendors and providers (I.E. Dell, Microsoft) and they're ready and willing to help in real time. Example: Our ISP and collocation provider was having trouble connecting to a hosting provider called ThePlanet out of Texas. Rather than calling and sitting in some queue and talking to someone in India, I sent a message to ThePlanet's Twitter account and learned of peering issues with my provider from a real person - total time to resolution: three minutes. If you like IRC, you'll like Twitter. It's IRC on a global scale.
Yes, Twitter has its share of spam and self-proclaimed "social media experts" but what social networking service doesn't? We get that shit on CR at different levels. Twitter makes my job easier, life more fun, and the hours I spend online more interesting. @cgreenoh