Pros
Looks good on your resume when you find an employer that wants to keep you long term. Positions in IBM customer facing roles build skills that will greatly benefit you in your next job, and you may learn how to recognize employers that you do not want to consider in the future. IBM still has excellent products and these are worthwhile assets in your kit for future employment, especially if you are technical, and for pre-sales technical roles they still provide time to get and keep those technical skills. You still get to work with some of the finest people in the IT industry, though they do not tend tend to stay long any more once they understand the way IBM views them and their compensation.
Cons
Lower pay than other companies, benefits in a death spiral and management lack of respect for the employee. Compensation growth is non-existent, in fact likely to be negative regardless of your performance. If you are not in a customer facing role your job is most probably going to a low cost country, though it may not happen quickly (IBM is accomplishing this slowly so it does not attract too much media attention). A mobile workforce, as IBM has, often means working alone without support, and without adequate tools. IBM expense and infrastructure policies mean spending hours a week accounting for travel and activity, which if you have service level agreements must be done on your own time.
