Pros
You will be surrounded by absolutely brilliant analysts and low level managers who are friendly and want to help you learn and succeed. If you are a researcher/analyst you will gain exposure to and experience numerous industries and methodologies that should prepare you for a high paying job in management consulting.
Cons
Low salary Poor culture - Hanover wants you to think it's a fun "start-up" like place with corn-hole, ping pong, and happy hours but the reality is that tight deadlines and a never ending workflow sucks the fun out of everyone and creates a toxic workaholic culture for below-market pay. Although deadlines and workflow can create a poor culture, low level managers frequently encourage analysts to take a break or stop for the day if they see that an analyst is working really late. This helps create a good work/balance in a no-fun workplace. C-suite managers are cowardly, dodge questions, and poor leaders in straining times. Low and mid managers are fantastic.