Pros
One of the first annual meetings I attended, they listed the people who had been with the foundation for 5yrs & 10 yrs, respectively. I didn't realize until a colleague pointed it out, but the list was almost entirely composed of admin staff. Benefits are great for this sector (retirement savings, travel, etc), but the shelf life of most staff (save admin staff) is about 2 years. On balance, some very talented and smart colleagues with challenging work that is not constrained by resources (not your typical NGO). Seattle campus is well designed.
Cons
I worked as a program officer for the foundation for six years. The mission statement of the foundation is that "All lives have equal value." The largest irony of my work experience at the foundation is that the internal motto should be, "All lives have equal value, except if you're a contract worker, admin staff, someone without direct access to senior leadership, or has Bill and Melinda on speed dial." Your value in this organization is in your job title, and everyone acts accordingly. My short summary: If the work doesn't kill you (they extract as much out of you as possible b/c you are very replaceable), then the work politics will. Just as the foundation is not a perpetual funder, it is NOT a perpetual employer. The work culture and environment is designed to ensure a half life about of 1.5 years for most employees. For an organization that can afford world class technical talent, it's HR division is possibly one of the worst I have witnessed (and I worked in government for a brief period of time). I believe this is by design as a completely incompetent HR division ensures no one sticks around too long. In fact, there are almost no paths for career growth as they expect your shelf life to be less than 2-3 years. One of the pros I list above in terms of resources (and there is a lot of it floating around) creates some of the most bizarre office politics. Type A people (almost 80% of the staff) will trip over themselves to control and command those resources, and if you're in the way (which you mostly are) then you will be thrown under the bus in the name of someone else's glory. It happens often. The first signal I knew something was deeply flawed in this work environment: the marker of a successful team meeting was that no one walked away crying (literally). You will be rewarded for "managing up" towards the senior leadership, but there is almost no accountability for how you manage down or within a team. Kiss up and kick down. You will survive well if you follow this simple principle. In the end, I did a lot of work -- some of it meaningful, but i feel much of it was a lot of hot air pushed by people who wanted to make a mark for themselves in the two years they would be spending at the foundation. This myopia is shameful but omnipresent. But, the organization seems to thrive on it b/c it has the resources to entertain so many vanity trips.