Pros
With Fast, you are relocated to a client's site to be available for support. This comes with many benefits if you are looking to fulfill some wanderlust. When moving to locations where the cost of living is particularly high, Fast does an ok job of ensuring the new location is not a hardship. I specifically chose 'ok' here because everyone is different, and fulfilling each employees needs is unreasonable (eg: my two top priorities for happy living could be wildly different than any other employees, and thus may not be considered).
Cons
Fast is hiring many new employees, and along with growth comes bureaucracy. New rules and regulations are created, but not communicated. This results in HR and accounting departments treating employees poorly because they are not following rules they don't know about. Some benefits are being deprecated, which is demoralizing to employees who started when they were still being promoted, only to find out that they won't ever see the fruition of said benefits.