DON'T MISS A THING
Slack was designed as a cross platform, customizable means of communication between you and your team. It brings together all kinds of work-related messages, files, and alerts, Often things that bogs down your email and messengers everyday. Think of slack as a searchable archived chat room, with the ability to communicate and interact with outside services like Dropbox, Google Drive, Hangouts etc...
Slack is composed of Channels, Direct Messages, and Private Groups.
Chat and direct messaging are awesome, but, the integration of Search and notifications pushes it over the edge. Getting Direct message notifications from team members on slack with push on my iPhone, keeps everyone in the loop and can also fine tuned in slack as to what you receive notification for.