Pros
You will have possibilities to work on multiple topics and learn new skills. Taking responsibilities is often encouraged and you have a chance to shape your own work. It is a research institute after all, so you'll get the benefits of working in a such place. However, it is no university, so expect it to be much more closed environment than educational facilities.
Cons
Management is out of touch and often nowhere to be seen. Many team leaders and managers are external hires, so they have little idea what actually happens in the field. It is also common to end up working in so many projects that you'll have time for none of them. Depending on the team leader you get, you may or may not get any support or direction in such situations. The level of science is also a mixed bag. Some teams are on top of their game while others are way past their best-before date. Consultancy work is currently encouraged, which suggests this trend will not change any time soon.