Pros
They have an open-minded more liberal approach to employee operations compared to some competitors
Cons
Any company is only as good as the department you work in. I worked for some great managers, but they were under someone who I felt was not good at all. My great managers moved on and were replaced by someone who had actually nearly been fired from his old position, but escaped it by getting hired in this job instead through sheer nepotism. He had no experience in the position at all but was friends with the managers who wanted to save his job. I feel this is reprehensible behavior and another example of how it only matters who you know. This manager was naturally horrible at the job as he didn't understand any of it and the department seemed to be going quickly downhill without any vision. I don't know what happen as he immediately made it clear I wasn't welcome and quickly pushed me out. I do not expect this is the norm at BlackRock, but it all depends on where you work.
