I did it. There are two IB schools in my area.
I got the diploma. My elective was art, they chose the world lit papers for us, and my extended essay was about Allen Ginsberg. My teachers all hated it and felt like my parents were absolutely terrible for letting me write about a gay Jewish communist.
I don't know if I would do it again. Being in IB forced me to become very organized, but the whole curriculum (at least the way it was taught in my area) was terribly constrictive. It made my first year at college a breeze, but the 40 of us were so competitive with each other that it made for a very unhealthy situation.