Pros
Since I agree with most of the pros already listed (especially the benefit of working with smart people), I'll try not to repeat too many and focus on the Research Associate role. From the start I was treated like a research partner- not just an assistant. In my experiences I have always received honest feedback. I've worked with great mentors, both within and outside of my team. They worked with me to define my goals and then gave me projects that would help me achieve those goals. However, its important to note that capitalizing on the opportunities starts with self-motivation and taking the initiative. It can be intimidating to speak up in an environment of experts, but it can go a long way. In this role you have access to industry and business leaders; and there is a lot to learn if you are willing to start by pushing yourself.
Cons
Development and coaching do not seem to be consistent from team to team. Not having a cookie-cutter approach allows managers to coach in their preferred/best styles, but it means not all RAs receive the same level of developmental help (but there are a lot of people at Forrester that are passionate about helping RAs in their careers- so taking initiative to seek these people out goes a long way).