I've spent time owning and moderating Teamspeak and Discord servers due to being on a ranked MMO team some time ago. Since I've also got extensive forum mod experience during the 90's/2000s e-wrestling boom using this very software, (vB) I figure I'll chime in.
1. It's largely used as a voice chat space. It helps people coordinate during games. If I'm a raid leader and I've got 20 people playing the same game at the same time and going up against a single raid boss, if we couldn't speak to one another in real time, we'd have been hosed.
2. You can set up different channels in it for different topics or different teams. (ex. If the guild I'm in has two teams going at the same time and a bunch of people chatting while we're streaming the attempts; you don't want people interrupting or overhearing the non-relevant conversations)
3. I've seen it used as a general chat room space as well, as the feature is supported (hey folks, we're having a chat about X in channel Y.. if you're bored in whatever channel you're in, come chat.)
4. It shortens the time to discussion. Topics will go from three to four days of discussion down to a few hours to one day. People can get to know each other better (we all know that's both a good and bad.)
Now for the bad.
1. People can be absolute jerks in unmoderated channels with no password. If a mod isn't online and someone decides to be a jerk (which would NEVER happen with our community) the users will hate life and the owner will hate the outcomes.
2. You need to set up a moderator schedule to have someone online at all times (peak hours especially) to handle reports of bad eggs.
So if you're going to do this, get a server for 10 bucks a month and no contract. Set it up and play with it. You're going to quickly see the good and the bad.
Thanks
KB