Pros
The people here are genuinely nice and caring. People do try to do the right thing in general and are dedicated to their jobs. The work-life balance is great, especially in the post-covid world, and I think people are really good at working remotely here. Also, I want to point out that this is a big company, so the stuff in my "cons" column might be a departmental issue.
Cons
One of Slack's core values is "collaborative." However, the way managers measure performance encourages division and siloing. The only thing that will get you a promotion is being the "DRI" for an important project. Everyone works alone unless they're an associate SWE or they need something, and they do try to help each other because they're nice and caring, but the incentives are to pull separately, not together. Surprisingly, Slack apparently does not, or does not always, collect direct reports' feedback on management as part of their review process. Weird!