Fidessa's U.S. operation grew significantly in the last decade, and recently went through a bit of a contraction with lay-offs. While not necessarily a bad thing, they now pay more attention to controlling expenses (i.e. employee salaries) than when the business was growing. It's also not quite as friendly a culture as it used to be.
Advice to those considering working there: Use Fidessa for personal career gain, and keep yourself available in the marketplace. They don't want "lifetimers" as employees.