Before I made a Twitter account I seriously doubted the usefulness of the resource. Why would you want to be limited to 140 characters a pop? What can Twitter do for me that Facebook can't? While Facebook can be utilized in much the same ways as Twitter, Twitter does its job better for certain groups of people.
I have conversed with several prominent members of my field through Twitter. For names most people recognize, this is difficult. But for higher-ups in a specific area such as SFF writers, this is sometimes easy. I have conversed with the likes of Brian McClellan, Caroline Yaochim, Mary Robinette Kowal, and Dan Wells on Twitter. I am followed by novelist David Farland (a pen name for Dave Wolverton) and short fiction writer Alex Shvartsman, among others. Many of these sorts of folks will respond to direct questions and some comments, assuming you're being civil.
I've learned a lot from reading tweets and clicking on links to posts and Google Hangouts by writers of speculative fiction. Some more specific information I've garnered from talking to lesser-name writers directly. They really are quite nice, in general.
Twitter can be a great tool for writers. It can be used for both networking and for gathering information. I do not regret making an account whatsoever.