I think in many ways discord hits it's peak when it can separate easily into multiple voice channels each with about 4-10 people each. I really like nested voice channels (like Mumbles linked channels) but really they don't show their benefits until you're deep into more complicated stuff (raids/etc) then the average person hits.

I think discords biggest (gaming-related) pull is that it's so simple to onboard someone. Once you get someone through the "two clicks" of on-boarding, it's much easier to get the them to say, especially since it's cross platform.