Pros
Overall tries to still have a fun employee culture although that has decreased since the merger (versus Metavante in MIlwaukee as a stand-alone company) Again, depends on what your job is but if you work in a 'corporate function,' I think you have good visibility and networking opportunities that facilitate future moves within the company (i.e. if you wanted to take on a new job in another department, then you would have the credibility built up to do that)
Cons
The social culture that Metavante had and FIS still has mostly can also have the downside of feeling like high school - politics, the 'in club,' office gossip, etc The Milwaukee location has changed significantly in the last year or two as it is no longer the corporate headquarters - and employee satisfaction also decreased sharply as a result