Ernesto from https://slackline.io here.

It's definitely working for us.

We have hundreds of companies collaborating through Slackline. From investors and startups, to agencies, consultancies and universities. We've been growing nicely since we launched.

With that being said, our objective is to cover much more than just Slack. It's a great platform to start with, but we have had vision that goes beyond Slack from day one :)