NASA is a bad sponsor due partly to unclear, shifting priorities but mostly due to inadequate funding for unmanned missions and research. Projects, lab facilities, and R&D efforts are routinely underfunded and success comes in large part from people putting in substantial amounts of uncompensated overtime. The environment is "entrepreneurial," which means you may spend substantial amounts of time lining up your own work rather than relying on management doing that job. Due to poor funding and shifting priorities, many efforts get started but never completed. Sometimes you can get in a mode where you're constantly proposing new work, hence the slang renaming of the place as "Jet Proposal Lab."
Since JPL has a good reputation, many people want to work there. The demand for jobs is limited and so the compensation tends to be lower than at comparable institutions. Average raises are typically less than inflation.
In many cases it's more appropriate to think of JPL as a "soft money" environment rather than a government job and you may find yourself constantly hustling after small and fleeting pots of money. Before accepting a job, consider having a discussion with your manager about funding levels for your projects and if you'll be expected to secure your own funding. Generating your own funding is not easy and usually comes only after years of building your reputation by networking within the organization and cultivating relationships with headquarters.
