Pros
There are numerous internal positions available which allow you to switch jobs or directions within the company. This is very interesting long term or if Personal circumstances change. IBM has good tolerance for Experienced Professionals who want or need to step off the social ladder. As a person who worked independently in the same job too, you need to get used to it. If you are young, you can climb the social ladder. If you are an experienced Professional, you are able to function and continue to function in such a role if you can sustain the continuous expected professional growth.
Cons
The size of the company. due to its size, a lot of regulations and restrictions are in place, which sometimes prevents some personalized treatment. During recruitement, I was "downsized" from a "Senior Managing Consultant" to "Managing Consultant" but was not told that the promotion to a higher rank was regulated and required extra certification. after 3 years, I am still not back at the "Senior Managing Consultant" position I had postulated for originally, due to the enourmous red tape. especially if your salary is/was on the top of the Market in your band,it is hard to get a financial promotion or a higher rank.