Pros
A lot of brands, units, and an infinite amount of projects with great flexibility to move among them. This enables employees to change roles and move into new projects. Sometimes this even happens when the employee has no previous knowledge or experience on the new area. Stable company, very focused on earnings and always with a vision for more growth.
Cons
We all work for the company stockholders. This seems much more like a financial company than anything else (service, it, etc): everything is calculated and there is always a cost/risk pair to it. Companies nowadays call their employees "resources", IBM calls them "cost". Too deep hierarchy. It's hard to know what is going on up there. Managers are moved from projects/areas/units/brands every 2 years, so you get a new manager who might or might not know about your project and how your team works... this is usually really bad. As always, there are some exceptions.