I was also at the Open Day, and I walked away with a very good impression of the school. Yes, it is expensive - but like nearly everyone (including GPPI, funnily enough) keeps telling me, there's no better place to study policy than in DC itself. So many NGOs and other organizations are headquartered there, which gives me the impression that it would be easier to get a good internship during the school year. I love all the international opportunities they offer, and I felt the staff and faculty were all really friendly and welcoming.
With regards to scholarships, I overheard one of the staff members saying that GPPI doesn't have as large an endowment as other schools, hence the low scholarship offers. Don't know how accurate that is, of course, but it makes sense.
Obviously, the above is only my impression, but I'm pretty sure I'll be going to GPPI next year.