Avantages
The group I work with is experienced and professional, and we get along well. Current manager is probably the best I have ever worked under. Benefits are about average, or possibly a little better than average, but the health insurance is more costly than one might expect, mostly because it is pretty comprehensive. If you are flexible in your tech skills, it is possible to move around in the IT organization.
Inconvénients
Like any large publicly traded company, your experience will depend entirely on the particular group you work in. Overly-reliant on IBM for infrastructure. It's a mixed result, with some groups being good and professional, and others less than useful. Stock market likes the new CEO, but a new CEO might feel a need to mark his territory some time in the next year or so. Government changes in health insurance regulations make everyone in the company a little jumpy.