Pros
Very good work-life balance. Good retirement benefits for employees who joined a decade earlier. Good enterprise-level technology - IBM thinks about "frameworks" that others can use. Very good reputation in the industry - "nobody got fired for buying IBM" still applies. IBM also has a very good follow-through with customers - once they sell a product, IBM will do everything to keep the customer happy. So it's a good company ethically for customers.
Cons
Compensation is below par with the industry. The problem with current "work-life" policies is that it holds back people who are willing to put in the effort it takes for career advancement. In my estimate, about 6 of 10 people in every group assume that flexible hours mean flexible work - and so the whole group is dragged down because the product doesn't get released on time, or features get left out, or quality is lacking. IBM is coasting along on the achievements of great people who worked there in decades past. But with budget cuts in areas like training, tangible and intangible benefits (2 and 3% raises, minuscule bonuses if any), IBM is losing its way. The current crop of engineers will not sustain IBM past the next 15 years. It's a great company for customers, but not so great for employees.