It's usefulness largely depends on the availability of accounts of the people who influence you and may influence you in the future. If you can build up a good network (and that takes effort), it really shines. I'm probably a "people person" so for me it really works.
Given all the stuff I have going on in my life, it's good to vent and, for some bizarre reason, I have received a huge amount of support along the way via friends I first met on Twitter. And yes, I now know many of the pepper I follow in real life.