Pros
You don't have to be very good to do well here; it's nice to know that you don't have to perform at 100% every day to do well. It's actually commendable that you can have an "off season", maybe something in your private life is dragging you down for months, and at Kaiser it's OK. Another genuince pro is that some of the work Kaiser does, such as the Community Benefit organization, seems genuinely altruistic toward the communities Kaiser is present in and is the sort of thing more big companies should be doing.
Cons
There are quite a lot of downsides, although none of them absolute showstoppers (so I'm still here). Kaiser is an opaque bureaucracy worse than any I've seen elsewhere, and that includes government organizations in the 3rd world. The culture reveres the idea of "partnering" and consensus seeking, which in practice seems to almost guarantee a lack of clear decisions or paths of escalation for problem resolution. Problems and issues don't get resolved at Kaiser, they just linger and morph and come back every year, with a slightly different twist. So there is a huge and unending amount of re-inventing the wheel here. I think top management is aware of these problems, and there are growing attempts at reform. However, much of the middle and senior management in Kaiser is dominated by a sort of "old girls network" and this network does not want change. They're comfortable, counting the days to retirement, and since change would take them out of their comfort zone, they steadfastly resist it. Too much of the work and budget within Program Offices is ultimately decided on the basis of personal relationships, and not on the basis of quantitative measures. Honestly I don't think a lot of the P.O. management understands common accounting measures, I know for a fact that many cannot compute a simple ROI (return on investment), which is a travesty.