Pros
Surrounded by smart and creative people, empathic manager, decent salary, very good benefits, flexibility in work schedule, having IBM on a resume
Cons
It's a huge company - lots of inertia, any sense of job security does not last long, any 'pro' listed above is totally dependent on the team you are on and who the director and VPs are higher up in the org chart - one person could have a great IBM experience while it can be completely awful for another person. People are often more concerned with self-preservation than producing reliable, consistent products and experiences. Tight budgets, reasonably high-attrition that often does not result in the role being backfilled.