Pros
The work feels meaningful and useful. Everybody working on Unity cares about Unity, as a product and as a company, and it's great to feel like you're truly collaborating every day. I get to travel to offices around the world, and make friends in different cities. I love the people I work with; my team are amazing, and my team lead is helpful, knowledgable and supportive. I feel respected and valued, and I don't feel like I have to tread carefully around people further up the chain of command - it's okay to tell people if I think they're wrong about something! There are active conversations about how to improve diversity, from company-wide initiative to small grassroots action taking place in individual offices. Unity is also great at providing support when people have stuff going on in their personal lives that might affect their work.
Cons
The employee experience seems to vary a lot from team to team, and there isn't a lot of accountability for team leads who encourage crunch or otherwise make work stressful for their team. If you were interviewing for a job at Unity I'd recommend asking about the team's culture and the team lead's management style.