Pros
More stability than most companies in the IT industry. IBM offers flexible working hours, a true commitment to working remotely, and the tools to empower remote employees The company offers solid benefits, and because it touches all areas in IT, employees do have a chance to experience different areas.
Cons
The communications function is highly bureaucratic, highly political, and overall does not necessarily reward the most competent employees, but instead ones that fit a specific HR box. All companies have to deal with this issue, but it's especially bad at IBM and in the Comms function. It is not a function where young comms professionals should seek to work, although if you have at least five years of experience and want a big brand name, I would recommend IBM only as a short-term (three years) assignment before moving on to another company to leverage your skills and knowledge. It is not a place to plan a career.