I'm a current GWU ESIA student and I'd say that your impressions are about right. The school's administration is definitely unimpressive, especially in regards to the admissions and advising offices. The students are about 20/40/40, that is, 20% are incredibly impressive, articulate and will go on to do great things. 40% are what you'd expect from a school with the location and ranking. 40%, well, let's just say you wonder how they got there.
I've been most impressed by the breadth of classes and the quality of the professors at ESIA. Seriously, I've had some great classes this year with top notch professors with incredible credentials, those classes have made it all worth it.
If I could sum up GWU/ESIA, I'd say you'll get out of it exactly what you put into it. If you put in to the effort, you'll walk out with top-notch recommendations, a great education, excellent peer-contacts and competitive for any IR job/program/fellowship in the country. If you don't make an effort, you'll be one of that bottom 40% and feel that you've wasted your money.
Given the amount of funding you've gotten, I say it's a no-brainer. For what it's worth, I was admitted to GT/MSFS this year (I applied for some complex reasons, don't let it make you think I was unhappy at GWU) and I'll be turning them down to stay where I am.