Pros
Gallup has an amazing research machine with excellent vehicles for getting that research to the market. They are in many ways thought leaders when it comes to the emotional economy and will be for some time to come. The employees of Gallup are amazing and I will take many of their friendships with me. Finally, Gallup is a fabulous brand to have on the resume.
Cons
Gallup doesn't respect their people. This mostly family owned organization has moved beyond the legacy of their father and into a mode of grow bigger and make more money at all costs. The quality of hiring that Gallup has been doing to replace the droves of long time employees that have been leaving leaves something (a lot) to be desired. I guess ultimately the biggest downside to Gallup is that they lack integrity. If you do decide to turn the other cheek, Gallup will pop you on that on as well. If you do decide to move on from the "tribe" don't give Gallup the courtesy of a two week notice, as they just dismiss folks without pay or benefits. While Gallup uses its tools internally, they don't do what they suggest others clients do (e.g. action plan or really listen). If you raise your voice in opposition to the strategy of the week, expect to find your way out of Gallup shortly, constructive criticism at any level is not tolerated. Finally, roles and titles are inflated on the business development side while the consulting side sits with lower titles and comp for their efforts. If you are on that side, you are likely being underpaid by 15% from market. Gallup was on top of the world when I joined, and has found a way to continuously drop as if it were a rollercoaster that never climbs.