I worked at ACI for over a decade. If you are able to get a job at the towers (i.e. investment management, IT, HR, etc.), I imagine ACI is an amazing place to work. If you are in operations or the call center, it is considerably less so. Past a defined career path, it is virtually impossible to advance in client operations; if you want to get into an entirely different area, the odds are even lower. Work-life balance is nonexistent. Once you reach the mid-range salary for your grade level, salary increases--including cost-of-living--cease to occur.
Benefits are good, but steadily declining. The only healthcare option, for instance, is a high-deductible health plan.
Wonderful people, free on-site gym, good employee fitness program, Up to $7K match for charitable donations or volunteer hours
Health care, work-life balance, lack of opportunity, lack of salary increase