Pros
There were some very bright and enjoyable people in the Gallup talent pool during the time I worked there as an Engagement Manager. I have heard that the Irvine, CA office is a good place to work.
Cons
Very few people stick at Gallup. Almost nobody from my Consocciates class still works at the company. The DC office is rife with bad politics. There are two sets of rules, one for favored, tenured employees and another for the rest of the world. Unfortunately, it isn't presented that way... more like you can chart your own career, be your best authentic self, succeed on your terms and work a flexible schedule. All of this is complete rubbish and will get you canned faster than you can say 'fired'. DC was like a revolving door with long term senior management and the rest of us, who were minions.