Pros: It's a big organization, but most of the work is structured around small teams. This gives you the benefits of having a fairly organized infrastructure for your work (HR, tech, communications, office services, etc.) while also having the ability to influence your team's work and take leadership on that level. This is also really nice socially. There are a ton of really wonderful people, and if you want to have friends at work... but with whom you don't *work* with on a daily basis... it's a perfect option. The people at the Aspen Institute are passionate and driven to make a change in the world. On the hard days (which you'll get when you work anywhere), it's nice to be surrounded by people who are outwardly motivated. I definitely was given professional development opportunities (though I get the sense that is team based... more on that in the cons). I felt like my boss was invested in my success as a professional. The benefits are really good, especially the retirement package.
Cons: As mentioned, although I got professional development opportunities, I think it was because I was lucky enough to be on a team that supported those opportunities. Your program largely determines salaries, promotions, etc., with only minimal oversight from HR. This means professional development opportunities can vary a lot depending on which team you're on. Also, at times, it's easy to feel disconnected from the people you're serving. But I suppose that's all part of working in a think tank, rather than in direct service.