Great team and benefits but don't get stuck
Pros
The Broad does have a strong culture and values, a lot of people love working there. The benefits and location are great, and there are great opportunities for scientific collaboration and Broadies have a vested interested in maintaining their affinity groups. Depending on the team you join, people stay for as long as 10 years.
Cons
Your experience can vary depending on the platform you join. I joined because I wanted to learn how to be a project manager but I joined the wrong team. The teammates were lovely but the work was atrocious; it was boring and pointless and leadership had no interest in optimization. Some people were overloaded with projects then chastised after asking for more resources. The work is not real project management and it sets up employees for failure if they want to look at new opportunities.