Pros
You'd better love your work, because it's all you'll do. The firm doesn't bother much with teambuilding, recreation, or enjoying life outside work in general. That can be wearing but if you're an up-before-dawn dynamo who lives to work, it's the best place in the world. More of a meritocracy than most places, more ethical than most financial firms. They were very good to me in terms of benefits when I was rehired there, crediting me all my back seniority time when considering vacation time. Professionalism is at a high standard, and you'll be working with the finest people anywhere. They are open to flextime schedules and have great maternity benefits and pretty good severance packages.
Cons
For an executive assistant, you're at a disadvantage if you want to grow within the firm. It's not encouraged, and for those few who did, they were always the first cut in layoff times because they didn't have the illustrious backgrounds of their peers and were always perceived as being of lesser worth. I saw that happen 3 times.