Pros
Technical breadth and customer opportunities are hard to beat since IBM still is one of the largest tech companies in the world. If you can find them, there is an IBM expert on everything (kind of like the Federal Government)
Cons
IBM used to a stable career choice, but with Resource Actions an annual event for the last five years, its hard to imagine being able to last long enough to retire or even make a difference here. The typical IBM employee now is a new hire, lasts 1 to 3 years (just long enough to show one or two stable roles on the resume), then takes the resume to get a job somewhere else. The first and apparently only response to negative financial quarters is - do an RA, freeze hiring and salaries, eliminate training and customer travel, shift work to lower skilled, lower paid resources, shift work offshore.