Pros
The biggest pro is your coworkers. You get to work with incredibly smart, fun, motivated people. As most of them have really long working hours, you are very likely to develop deep, lifelong bonds with your companions. You may also learn a lot about development, data analysis and econometrics (depending on your project), and hone your leadership skills. Some of the researchers in IPA are top professors, and if you do a really good job you may get an outstanding recomendation letter. No dressing code and flexible hours too - as long as you are fulfilling your project's objectives.
Cons
Highly demanding tasks in terms of skills and time. For a 3-4 months period I had to work until 11 pm regularly, even on weekends. The same happened to most of my colleagues. There is an implicit expectation from managers and even from not-so-few researchers that the RAs will work as much as the project needs it. Extra hours are usually not paid nor compensated in any way. Some projects have impossible budgets/timelines/objectives, mostly because managers have not planned them properly or because reasearchers have unreal expectations about what job in the field is. You have to learn how to manage-up these problems.