Pros
There's a breadth of teams that do different things with varying cultures. I liked that I was able to choose a team that suited me best when I went through the new grad rotation program. I liked that MongoDB is very invested in its intern/campus program. As a result, there's a good focus on making sure that you are getting the most out of working here. The people who work here are smart, humble and are overall great to work with!
Cons
I haven't really noticed anything specifically bad about MongoDB as a company. However, depending on the team you're on, I've noticed that sometimes it's hard to get recognized for the work you do. If you're on a larger team, you need to make sure that you are actively promoting the work you do.