Pros
Large company, likely to stay in business. Unfortunately, there is no stability or security; there appears to be a constant drive to exploit employees by making non-professionals exempt, reducing vacations, and benefits. Exempt folks are required to work 10% overtime. Managers are kept away from their employees -- it is much less stressful to lay someone off if you have never met. Even "teams" are assembled from distant locations, creates less emotion when someone is "disappeared". There is no company education -- early in the year, there is no budget; later in the year, there is no time available. Not the great company IBM once was; Sam sets the tone.
Cons
Working at IBM is like playing roulette. Whether you have a job day-to-day is like spinning a wheel; your continued employment has nothing to do with your abilities or competence. I met my last manager face to face for the first time on the day I left the company. I had worked for her for two years.