Pros
The best thing about Waterfall is the incredible team you get to work with. It's still small enough to not only know everyone, but build professional relationships and friendships with everyone. From an engineering perspective (that's the team I'm on), it's really easy to carve out an area of expertise where you're given ownership and accountability over. We're free to try out and use bleeding edge technology to realize our projects. Not a lot of red tape, just get things done. The culture is pretty great too. We spend a lot of time together outside the office doing various fun activities. As a result, I think you see a lot of genuine camaraderie between employees.
Cons
The company is growing rapidly which is resulting in some growing pains. It can be hard to keep up with all the changes and new faces.