Pros
Relaxed work environment, max 50 hours a week, hour lunches, benefits im told are good. Great place for people to claim they work in finance (it is not, it is mindless button pressing / mouse clicking in the back office with no need for intelligence and no client interaction - and the street knows this). I will however say State Street is a global bank and their front office departments (Global Advisors, Global Markets) are highly regarded in the industry and provide great learning opportunities (and substantially higher pay).
Cons
No career advancement opportunities - advice to prospective employees is to not take the job to begin with. Advice to current employees is to get out as soon as you can. The longer you stay at back office, the longer you will stay in back office despite false optimism instilled by management that State Street will provide you with long term career development opportunities - moving within back office isn't career development. Extremely low pay. Almost laughable given people 15-20 years older would make the same $ amount salary in their first jobs out of school - do the math - 3% inflation every year for 15 years...assuming a 40K base for those guys you'd need to be making 62K to "break-even"...not happening at State Street.