I wouldn't say that it's "hot". It's recently become more popular since Google started forcing it on Android 4.4+ users as the only SMS option on their phones. Personally, I wouldn't use it at all if not for easy group communication with my Ingress mates (most Ingress communities use Hangouts, Slack, or both; ours uses both but mostly Hangouts).

I just felt that it was a glaring omission, especially considering its more popular and more reliable precursor, Google Talk.