Pros
Largest technology company in the world. You could literally have a career in almost any field at IBM. Leadership happens here whether you like it or not. Which could be a good thing for people that aren't well equipped to be assertive and let it be known that they want those roles, but bad if they don't want leadership positions and end up performing poorly in them. I was a co-op at IBM while in school and worked there full-time after graduation and throughout both experiences my managers let me do my work without micromanaging. You're given a task and a deadline. They don't bother you too much before that deadline either, and I loved that! If you enjoy working from home or anywhere in the world for that matter, IBM is the place to be! I rarely had to use any vacation days because I would work from home wherever it was that I was traveling to (you can't party every single night!). I would go "live" in other cities and work from coffee shops or one of IBM's gazillion offices around the world. Speaking of vacation days, unlike other companies where you have to "earn" your vacation, at IBM your yearly allotment is available to you on January 1st!
Cons
The cons are, IBM's solution to poor financial performance is to "cut costs" and unfortunately they have no problem "RAing" (laying off) 6,000+ people at a time! IBM is over 100 years old and its workforce is not very youthful either. Coming in straight out of college I was in awe to be at such a "great" company but after about a year I realized the huge gap in the employee's "industry experience" and there's nothing at all wrong with that but if you're looking for exciting and fun, I hope you get your thrills out of lines and lines of code!