Pros
You will not find more interesting, open, well-read, clever, and downright funny people to spend a summer with. I flew out of bed at 5:30AM to come to work by 8 or 8:30. Extremely casual but hardworking and thoughtful atmosphere. To someone stumbling across the website with no prior knowledge and no interest in human freedom, IHS's mission could appear esoteric, but I happily vouch for how interesting, relevant, and down-to-earth IHS manages to make it.
Intern program was/is well-structured and you can get a lot out of it, intellectually and professionally. During my year, we had weekly reading discussions (a paperback book and a spiral-bound collection of shorter works) and, almost as often, a guest from an outside organization for lunch or a talk. I found my 2014 summer internship thanks to one of those guests.
It's also flexible. We were encouraged to be in the office when others were so that we could help out our respective teams, but there was no required arrival time in the mornings. I generally arrived at 8 or 8:30, but people trickled in until about 10:30. No passive-aggressive stares for arriving at 9:15. DC summers are a great networking opportunity as well, and I was always welcome to step out of the office for an extended lunch break to attend a talk or event on the other side of the city (foregoing $7.25 plus added metro fare ended up being worthwhile every time).
You get to do meaningful work as well. I saw a lot of the work I did go straight to seminars, and other interns saw their contributions (with credit given where credit was due) advance IHS as an organization.
I saw a lot of fellow interns who had finished college get hired at IHS or at other organizations at the end of their internships. It's a meritocracy.
And, once you're an alumni, the door remains open. I've been invited to Advanced Topics seminars, notified about career opportunities, and generally kept in the loop.
Cons
The quality of the internship makes up for the low pay, but you have to be really creative in order to live on that hourly intern wage in the DC metro area ($7.25/hour in 2013). You can work up to 40 hours per week, however. Having a side gig on weekends is not unheard of. Have parents who pay for everything, a serious affinity for living frugally, or considerable savings before starting. The salary doesn't pay for a room, Metro, groceries - it mostly subsidizes those expenses.
(Even if you were unpaid like Capitol Hill interns, you still have one of the best internships in DC.)
