Pros
Some of the things I appreciate about GSK, accountability, respect for employees, good benefits package, fair pay. Traditional opportunities and advancement are hard to come by, but that doesn't mean there aren't development opportunities out there. You need to take the reigns, no one will do it for you (I state the obvious because many people here seem to expect someone else to be managing their careers for them). The current leadership team is very aggressive, but they respect a work/life balance.
Cons
The industry is going through some big changes, changes that may take 10-20 years to work themselves out. Be prepared for that when choosing a career in Pharma. If you're not directly related to drug development and sales, this may not be the best place to focus your career. But that being said, people will always need medicine, so if your style is compatible with the leadership of the company, go for it.