Pros
Excellent people to work with. Good benefits, 401K match, managers are generally good about vacation. There are opportunities for career growth, but one must make it one of your goals to advance. The problem is people are so busy working, they don't spend time on planning their own career. Another positive in IBM are the opportunities to work on patents. Generally speaking, I found colleagues are bright and industrious. But it's not a place for slackers.
Cons
Just like anyplace, there are some good managers and some bad managers. Good managers open to improving the way things work, not just the way things look on a chart. Good managers also try to develop their staff and help them advance their career interests. Bad managers often look out for themselves, not for the staff. They will pressure people to make unrealistic goals; do not plan well and then work everyone into the ground when the plan is broken. Careerwise it seems to take a long time to advance unless you have been at the right place, or connect with the right people. But that's true everywhere.