Pros
Feeling of working for a big organisation. Its a lot bigger than initially thought of by future employers. Very foccussed and clear structure to do your job in, lots of training and support. Benefits are great, bonus, travel, healthcare, staff events, technology etc. Lots of diversity and exposure to a vast global network. They hire talented people.
Cons
Lots of egos, the politics are insane and can make it a difficult claustraphopic environment sometimes. Hard to reach career goals due to too many middle managers allowed to hold you back, HR needs more to have more leadership and development direction and moniior certain personality types. Future employers dont rate the GSMA much on CV, which is a shame as it is a great influencer and global organisation.