Pros
Flexible telework/schedule, good work/life balance.
Cons
Most people do not do their job and there is no accountability for it. The organization I worked for was very top-heavy, with lots of employees in the GS-14 and GS-15 range, so a lot of work landed on those of us at lower levels. Opportunities for advancement are almost nil. Performance evaluations were mostly a formality with most employees getting a rubber-stamped "satisfactory", and the only way to advance from one rung of the career ladder to the next was to spend adequate time in grade. This produced a general lack of motivation to do better or go above and beyond what was minimally required for the job. Bureaucracy was nightmarish, and the technology available was years behind. While GSA is generally thought of as one of the "innovative" agencies with its head in the modern world, that is really only true of a couple of offices and groups (like 18F). If you're not in one of those, it can be a suffocating and demoralizing place to work.