Pros
BJC Healthcare is unusual, in my experience, for a large company. Senior management is actually competent. In fact, the few members of management (director level and above) that I regularly dealt with are some of the smartest and most focused people that I have worked with. One VP in particular is good. He is the head of the Center for Healthcare Quality and Effectiveness. He tends to have good insight into whatever project is being worked on, or whatever problem is at hand. Please don't think that I normally praise the quality of senior management. Of the four professional jobs I've had, BJC definitely has the highest quality management. In fact the other 3 companies have ranged from moderately okay to abyssmally incompetent.
Cons
It is a large corporation that has a feel of a large corporation. There are a lot of rules and plenty of people that will complain if you break any of the rules. For instance, the dress code is fairly strict (business casual), but you can occasionally get away with nice jeans. But if you're meeting with certain people and it isn't a Friday, you better be careful to dress nicely or you will hear about it. As in any large corporation, there are plenty of people who just aren't good at their jobs. They attained their position through a combination of tenure and politics, and they don't seem to get weeded out very efficiently. Also, annual reviews are done in a "peer review" style, where all members of a department critique the work of their fellow employees. I personally am not comfortable doing that.