Pros
At the EPC, I had the opportunity to meet a wide range of people across different types of organisations (e.g. European Institutions, large corporations, business associations, NGOs, academia etc...). This opportunity allowed me to discover the work of many organisations and network with many people. The team does have nice colleagues.
Cons
As a programme assistant, you are essentially put on a freelance contract. It involves significant paperwork. With the social contributions you will have to pay, your take-home salary is less EUR 1,000/month, which is barely enough to make ends meet in Brussels, and less than a traineeship at the European Commission. In my experience, the career progression options are quite limited. This job gives you a foot in the door, but I won't expect to stay at the EPC for more than a year.