Pros
At Esri you work with a lot of very smart people at all levels, and generally the "power distance" between management and employees is quite small. I think many employees overlook the value of their medical benefits. We pay for our co-pays and deductibles as is standard with all plans, but we do not pay for our insurance. Most companies require the employee to kick in something per paycheck. And the coverage is generous.
Esri is a great place to grow laterally, but with a flat heirarchy there is little "upward" movement to a career. If you are a promising employee, you will be given more responsibility over time and will feel and upward trajectory as your influence grows.
Other reviewers have alluded to duplication of effort within the company, but that is part of its deliberate design. Jack wanted a marketplace of ideas similar to what you might find in an academic setting. This sometimes leads to friction as two groups attempt to reach a similar goal, but the point is for the best idea, the best approach, to come out of this creative conflict. It may not make us comfortable, but the success of the company sure validates this method.
Cons
Most people at Esri haven't a clue as to how to provide feedback either to each other or to their employees. Managers dread the review process and try to get through it with as little "drag" on their daily work as possible. It is not seen as an opportunity to help employees grow. Most managers believe that employees already "know" what their problems are and that those employees deliberately choose to continue with whatever behavior is undesirable. It never occurs to managers to be honest yet constructive in telling an employee what he or she should improve.
Management itself is not seen as a worthy way to spend the day. Middle managers are expected to spend their 75% of their day on "real" work and no more than 25% on "management." Their workloads can be crushing as a result. Directors (top level management) work just as hard, however. No one at a high level in the company is coasting.