I really liked this. I thought it would be creepy, but it turned out to be very affecting. The cast was excellent, especially the two girls. Well done Adam Rapp.
I liked it too, although my theater partner did not. It was my first exposure to Rapp. It took me a while to warm up to the play. I think that's because it's not very expository, and you have to wait until all the pieces are revealed. You don't even know what the characters' relationships are with each other, and what brought them together on that particular day. So it's very puzzling at first, with an undercurrent, as jbird5 said, of creepiness.
I thought the character of Monique was a bit over the top and cartoonish, which didn't fit in with the other portrayals and occasionally jolted me out of the proceedings. But I found the play ultimately very affecting, with excellent performances.
And it bothers me that in the title, there's no comma after Joppa. That's just wrong!