Providing value is not the whole story. That's why I begin looking for alternative factors -- like luck and circumstance.
The thing keeping HipChat going in the face of Slack is that Slack can't be used on-premises, which is HUGE for an extremely large percentage of business.
HipChat hasn't improved as fast as Slack because they haven't needed to-- since no HIPAA-compliant business (to give just one example) can use Slack at all, the two products don't really compete with each other currently.
That doesn't apply to this new Microsoft solution, which will probably kill-off HipChat long before it kills off Slack. Unless Atlassian really gets their butt moving and starts improving their product.
Even when the worked, Hipchat notifications weren't configurable a the granularity I wanted.
Slack also is prettier and feels more cohesive to me, but that's a secondary concern.