Pros
The international brand recognition of IBM is a plus. You don't have to "sell" IBM before you sell a product. The benefits are very good globally, although you pay for them. The allure is the ability to move within the company, gaining tenure and having multiple careers. Many people have done this and it is truly possible. Another good reason to work for IBM is that as a company, the training programs are superior. So, you can build skills, have access to much educational information and participate in mentoring relationships. IBM has been a leader in research and ideas, so people listen. There are some unique benefits like award trips, thank you awards from peers, special VP awards, etc. that really do recognize people. Having a good manager who will work with you to grow and place you in your next role is essential.
Cons
There are still many pockets of "good old boys." And, unfortunately, they still get away with things that most would consider bad, if not illegal in 2008. There is still a serious lack of communication between various matrixed management and this impacts answers' to employees questions. You may get a different answer each time. Another downside is the increased managing of earnings. Many sales people leave because of retroactive quota increases, the feeling that they cannot impact their quotas/ objectives and that there is no career path for sales. The account executives rule the roost and this is the epicenter of the good old boys territory. You will see few women in these positions and if you do, they are still openly mocked behind their backs. IBM touts values, but sometimes has a difficult time implementing these. They will protect managers above employees in all circumstances. Fairness and respect for the individual are lacking.