Pros
Getting the name on your resume, and you may learn something if you are in the right deparment. The company seemed very flexible in terms of letting staff take time off for personal reasons, one colleague getting six months off to go on a round the world trip. Good work life balance overall. Also, the company supports employees who wish to further their professional education.
Cons
The Commerzbank is a gerontocratically run institution...gray hair is the key to success here. Generally, there is a highly bureaucratic feel to the place, and there is little scope for autonomous thought. Also, it is a very conservative environment, though I guess no more than you might expect from a German bank. Oh, and salaries are determined according to a general schedule (like the one used for bureaucrats and army personnel in the US).