Riot is worth trying as a replacement for group chat and instant messaging.
Good things: As well as a web interface, it has fairly well made clients on all the main desktop and mobile platforms. Great, this is table stakes, yet so rare!
Bad things: Confirming encryption keys is a bit clunky. However, it's a new feature, and they're working on it.
Future promise: Riot is built on the Matrix platform - so the most exciting thing about it is that if it succeeds, it will also make other apps easier to build.