UT uses Blackboard as its LMS (Learning Management System), though they are currently piloting Canvas as an alternative. Many faculty are not fans of Blackboard but I don't really mind it. It does what I need it to do--store course documents and make them relatively easy to find; provide an e-gradebook and calculate grades. I have never used its discussion board features, though I've heard from both students and instructors that they are clumsy. Early this fall, just before the first review session of some content they had watched at home, I opened a thread on the discussion board for them to post questions for the TA leading the session. Immediately, a student emailed me asking if I would create a class site on piazza.com.
I have tried to approach every aspect of this course with an open mind and so figured that I should see what this piazza thing was. I browsed around and decided that it couldn't hurt anything and so created a site. It took about 5 minutes (though I now know I should have imported the class roster myself rather than letting piazza do it). The site itself is pretty simple and intuitive: students post questions which they can tag (thereby organizing posts and making it easier to retrieve posts on a certain topic). Other students or instructors can answer the question. I'm not sure why--perhaps the mere fact that it isn't a UT LMS--seems to have encouraged the students to feel some ownership of the class site and to participate pretty energetically. I get an email when a student has posted something (I've set it to be a two-hour digest). Typically, by the time I get to the question, at least one other person has answered it and often done a more thorough job than I would have (e.g. pointed the student to page # of textbook where topic is discussed or provided links to external sites).
Students certainly use it to ask basic questions that are, in fact, covered in the readings and recorded lectures. They use it to ask questions about course logistics (e.g. when will attendance grades be posted? when will we know our exam grades?). They also use it to ask questions that the readings and lectures provoke but do not address. That is, they use it to sate their curiosity or to extend a discussion. At times, I have used it to extend a conversation that started in class or to raise a related topic. I frequently get several takers who are willing to contribute their thoughts.
My absolutely favorite part about piazza? By encouraging students to post there (they can do so anonymously if they wish), my email traffic for the course has dried up almost entirely. I answer questions once rather than 34 times. I can answer their questions quickly, while they are still fresh and I can do it in a few words. It takes much less time to answer 4-5 questions on piazza than to answer 1-2 emails.