Pros
Enormous company with many eco-systems so employee experience can vary greatly depending on management and business challenges. I've worked there 8 years, rose from Admin to Manager and have been offered valuable professional development opptys most points along the way. In an HR delivery function I can attest to it being a very ethical company that tries to do right by employees. Employees must own their development but the tools are there and easily accessible. Movement is encouraged to build breadth of knowledge. Pay is good/fair and benefits are excellent.
Cons
Constant market fluctuations can drive waves of RIFs that cycle through the various businesses functions. Certain functions, like IT, have seen more than their fair share. That said, there are many who have been with GSK IT over 20 years. Not unique to GSK, but they continue to try to do more with less to protect stock pricing. Employees are feeling the strain. Too many simultaneous objects. Very project focused and too many meetings.