Coworkers are legitimately great, free lunches in office 1X and occasionally 2x per week, solid career path if you are on the fund side. Some of the clients are great.
Cons
If you are not on the fund side the career promotion options are relatively limited, I particularly felt that for the ISS position at times that your purpose was just to plug any holes that exist and your personal development was a bit of an afterthought.
The company is primarily a Fund Accounting firm so be prepared for long and grueling hours during the busy season (Jan-May).