Pros
I love Slack's focus on people. This manifests both in the focus we place on our customers - taking customer service really seriously, responding to every tweet, focusing on building delightful experiences - but also in how we treat each other as employees and coworkers. There is a level of respect and courtesy that is really special and leads to a really inclusive and supportive working environment. I also appreciate the balance that Slack provides. It's an enterprise software company that has a deep focus on building a human experience. It's a start up that values work life balance. We're passionate about what we're doing, but also realistic and levelheaded.
Cons
There are downsides to working at startups, but with that comes the opportunity to build something from the start.