Hard to describe. Very chaotic. Almost no Product Managers on my interview loop. Most of them were right out of school and didn't seem to know how to interview well. At least not for PM. The recruiter was very nice.
If you are over 30, then don't bother with this place. More than 50% of the company has been there for less than a year. While the CEO claims to value diversity, age/experience is clearly not something he values. Or, the company is growing too fast that they can't maintain the original culture.
Lots of young, underqualified, inexperienced interviewers who don't seem to want anyone more qualified than them around. Might block their rise. So, clearly, politics has taken hold of Slack.
One interviewer was overtly discourteous in the interview. Highly unusual behavior in my experience. This individual was right out of college and hasn't received much in the way of coaching.
Overall, pretty negative impression. Slack seemed to be the anti-bro unicorn in town. This might be true, if you are young enough to get hired.