Pros
The advantage of working for a large pharmaceutical are the broad opportunities available to employees for advancing your career. The benefits are good for employees. The salary and bonus is competitive with the best incentives for the lower salary grades. GSK is trying to create an image of a good corporate citizen in the aftermath of several well known regulatory compliance issues. And if you love open office concepts, then there's a place for you at GSK.
Cons
As with any large pharma, creating a strong corporate culture is talked about, but not organically cultivated. Having worked at smaller biotech companies, it is apparent that although they want to create a culture it is difficult for a large globally disconnected corporation to truly have a common culture. Innovation and thinking outside the box are trumped by bureaucracy and following the herd. My personal experience with HR is that they toe the company line and are not truly ambassadors for employees. Open office concept is not as productive as management would have you believe.