Great opportunity if you are in the right group
Pros
IBM is a huge company. You can have many internal resources to reach out to. It is also a great place to work if you are looking for stability -- an ideal situation for those who have kids in the junior, high school years. Many people at IBM are lifers and have never experienced work outside of the company.
Cons
Extremely slow in getting things done due to its size. People are very conservative and risk averse. Not an innovative company by any stretch of the imagination. The most innovative thing I have seen since I joined are things that other companies have done two years ago. In tech, that's ages. Management chain is huge. You have many layers of middle managers. As anyone knows, communication gets lost when you have many people in the chain. So, a lot of times people run around with little direction. First line and second line managers seem to be running the show, pushing down the work, and upselling themselves as they go. There is little to no advancement. Despite the message about growth opportunities, there is very little in the area I am in. No one has left (voluntarily) in our department for years. Most people are either going to stick around until they retire or they are stuck and can't get out. Either way, IBM breeds specialists (aka lifers) unless you somehow break out beyond the first line manager role. From what I understand, the air is clearer and better when you fly in the upper echelon. To advance in IBM means to leave the group you are in. In the three organizations I have worked in, I can only think of two instances (out of a total of over 150 people) where people were promoted to manager level from within. But they promote people to managers or straight hire from other groups or outside. Very discouraging for those wanting to grow from within.