My main issue with this new Campfire thing is that since it's self-hosted, my boss can basically read all my chats with coworkers. Sure, Slack's priciest plan lets them do that too, but most Slack setups I've seen don't bother. Plus, Slack itself isn't as likely to snoop through my messages about pay raises or thinking about quitting, unlike my employer.
I wish them the best of luck! I miss the buy once, own that particular version forever model, and I hope it works out so good that others start offering their tools with this model.