Pros
Cisco is organized like a series of small companies (Business Units, or BU's), brought together under a single umbrella. As such, there are many different opportunities and career choices available. Want to work on streaming video? Think that Java is a better choice for web interfaces than C? Have strong feelings about whether XML is really a good interface between cross-domain components? Find the right BU that is working on the technology, and a manager or tech lead who is open to ideas, and the opportunity is there. The engineering development methodology can be a pain, but it does insure that the project you are working on will not get cancelled after you've put in uncounted hours.
Cons
Your job satisfaction will depend on the abilities of the managers and tech leads in your Business Unit (BU). If the BU is led by non-visionary or agenda-driven people who are not open to change, then this will just be another job. Recognition may be based on politics or the buddy system, instead of competence, and ineffective managers will not want to rock the boat or get rid of deadwood. Cisco stock isn't going anywhwere, so options aren't worth much.