Pros
The team I work for is amazing - everyone works hard and is dedicated to creating and supporting our products. In general, the salary and benefits seem to be around the middle of industry-standard and the work-life balance is good. Also, Fiserv really does create some terrific products.
Kontras
Like many large companies, the bureaucracy oftentimes prevents employees from doing their jobs effectively. Also, decisions are made higher up with little or no thought to the ancillary effects of those decisions. And too often, "but that's the way we've always done it" is considered a valid excuse - many departments are risk-averse in the extreme and this prevents them from reacting in any way to situations that are unfamiliar to them. The result is that they freeze and do nothing - literally.