Pros
IBM is a large company with a long, established history. Generally speaking, people know who IBM is--across the globe. The global reach is an additional benefit: provides more stability in the crazy global economy and makes it veyr interesting in terms of working with colleagues in different parts of the world and getting their view of things.
Cons
The company is so large that it's very difficult to navigate. More importantly, the size becomes a greater issue as more of the workforce is remote. I've worked with people for years whom I have never met. Additionally, there is very little consideration of the issues associated with working with global counterparts: ie: the fact that the people with whom you're trying to meet/work are 12 or 14 hours apart.