Comprehensive list, thanks for sharing, definitely bookmarked.
Thanks ! Glad you liked it !
Not yet. We use Google Hangout internally and Podio for Project Management.
To be honest, Slack isn't for everyone. At my current company the excitement/usage of it plummeted after the first couple months. It's basically become our company-standardized IM client now... which is fine... but it's not like it's a game changer. InVision is FAR more valuable to us IMHO.