Pros
Job security, challenge, opportunities, variety, travel, big name employer, reputation, looks good on a CV.
Cons
Virtually non-existent management of it's people and what there is comes from a 'must-do-it' process. I spend about 30 minutes per year with my manager (because he has to). All IBM cares about is selling more services and profiting from pimping out its highly skilled employees to any big business with more money than sense and paying its employees as little as it can get away with. Like a great number of IBMers (horrible horrible horrible phrase) I was TUPE'd in following a penny-pinching outsource exercise which took a brilliantly run IT team of about 30 on-shore individuals from a large telecoms operator and offshored most of the roles to India. A year later, two thirds took the money and ran, a quarter are still there (deeply unhappily so) and a three of us took up new IBM placements. Predictably, outsourcing has now stopped at the operator as a result of poor feedback. The feeling of belonging does not exist at IBM. The only reminder I have that I work for IBM is when you see advertising boards at tennis matches saying 'IBM'. They couldn't give a damn about employees as long as they bring in revenue and keep their clients quiet. I could go on and on all day. Suffice to say, if IBM threaten to outsource your job, take the money and run.