Pros
The benefits are outstanding. I've worked in a variety of business environments and none of them compare to CoStar in terms of benefits or work atmosphere. There is a clear emphasis on health and wellness, from the fresh fruit, juice and snacks provided daily in each kitchen to free in-house yoga classes and a state of the art gym. The health benefits are great and we have regular health screenings in the office for free. There is also additional leave time provided for weddings and maternity. Someone starting at CoStar as a first job may not recognize how important benefits like this are, but this is above and beyond the norm, and CoStar continues to seek ways to add/improve benefits while most companies are taking them away due to the economy.
Cons
I think your experience can vary widely depending on who your manager is and the department you work for, but senior leadership is aware of that and actively working to fix it and create a more consistent experience for employees across departments.