Pros
At the Chicago office audit practice you get to have a lot of independence in your work. For many smaller clients you will be in charge of the audit within 2 years of starting. The office environment is fairly casual. All the managers and partners have their doors open. In the financial services group, you get to build relationships with the clients' executive management almost from the time you start. Generally if you put in the work, you will learn a lot very quickly. The starting salary is definitely in line with the big 4 in Chicago. At least it was a few years ago. I recommend researching the different groups in the firm, they all run differently because the partners running them pretty much do whatever they want.
Cons
Seems like the place is very disorganized. Although I hear this is the case at many firms, I still didn't like hearing "look at last years files" when I asked about how to do something. Pretty much I learned how to do everything by looking at last years files. Mentoring was almost non existent. Depending on the type of person you are the following may be a downside. In my case it was. The majority of the people at the 1S Chicago office are from small-town-USA and it shows. So if you are used to city people and interests beyond work, sports, and drinking beer, it's sometimes hard to relate to people beyond the work day.