Lots of opportunity but you'll really have to work for it.
Pros
Great people, well known brand, deep pockets, complex projects and good learning experience. Global reach means lots of opportunity if you're willing to travel. Reinventing itself in some really leading edge technologies such as AI, cognitive computing, cloud, deep analytics. Few constraints on work location or work style. Very wide array of jobs, can reinvent yourself and have many careers within the same company. Competitive salaries.
Cons
Complex and difficult to navigate Recently seen as "old tech", not a glamour brand Wall Street hates IBM and IBM tries to manage to Wall Streets needs over its customers and employees Leads to regular "Resource Actions" and divestitures which can be unsettling. People disappear overnight! Flexible working means constant working. Very easy to be sucked into an unhealthy dork life balance.