Pros
Kaiser is a great place to work and build a career over time. In my experience salaries are above market for most positions, and the benefits are so good that many people become "lifers". The health coverage is extremely generous, and time off starts off adequate and gets better over time (18 days when you start, moving up to 33 after 15+ years - this does not include sick time). Employees truly believe in the mission of KP (at least, I do) and it's clear that this is a place where employees' contributions are valued. Although my role is not part of any of the unions, the fact that our workforce is predominantly unionized also places a positive role in KP's reputation as a good place for workers (although having unionized staff also presents many challenges). Overall, I enjoy working at KP and would recommend it to others, but understand that you are entering a big bureaucracy. A friendly, mission-driven bureaucracy, but still.
Cons
Cons: having lots of "lifers" means that innovative ideas and workflows are not always adopted without a fight. People have their roles deeply embedded here, and any threat to the status quo is seen as negative, even though we need to make some pretty radical changes given the new health care environment post-ACA. There's a lot of "not my job" attitudes here. It's hard to navigate the layers of bureaucracy, both in terms of personnel/HR/benefits, and in getting work done (there are often 4-5 departments at the regional and national KP levels working on similar areas, and no guidance on who does what.) Be aware that KP is not immune to reorganizations and layoffs -- they do make a good attempt to ensure workers are hired elsewhere in the organization, but there are no guarantees, and there can be a lot of turnover in certain departments.
Benefits are currently generous but are always subject to downgrades in the future, so just be aware of that. Some changes to the pension and retiree medical benefits are about to hit, and with them a wave of Baby Boomers will be taking retirement, which should hopefully open up many new management opportunities for Millennials.
Oh, and the biggest con of all: we still - STILL - use Lotus Notes for email. Shocking, I know, but true.