Pros
Depending on the dept, they give healthy bonus but the salary is not competitive and raises are minimal. Good, recognizable, reputable company to put on your resume. They do hire best of breed talent and you will work with smart people but do not expect a life outside of work. Their motto, "One BlackRock" is becoming like the big financial corporations out there with lots of red tape to get things done. They are loosing sight on how they started off.
Cons
There are are clicks and you need to be in the senior management click to get recognized and promoted. If you're a worker bee and quiet, you will be looked over and will be given work no one wants to do. They promote work/life balance but expect you to do the work of 3 people so I question the validity of that statement.