Pluspunten
This is hard to answer because the culture is changing... I can say that it's great to have flexible working hours, a manager with an open-door policy, and many talented coworkers. Once you've been at Fiserv for awhile, it's unlikely you'll be let go unless you really screw up, so the stability and job security are positive factors, particularly in this tough economy.
Minpunten
Benefits are being slowly whittled away. First they eliminated the Sabattical program, then they changed the health insurance benefits (only high deductible plans are being offered for new hires, and the PPO plan will be phased out in the future), and next year they are going to give us PTO time instead of the vacation time + liberal sick time policy we currently have. Another thing about working here is that longevity matters more than skills, ability, or experience when it comes to being promoted. Fight for the best possible title and benefits package you can get when you're hired, because once you're on board, you won't see a promotion until you've passed the test of time. Meanwhile, people with lesser skills, who put forth less effort (and indeed, even incompetent people who don't do their jobs) will be paid more than you and have a higher seat on the food chain because of their years of experience.