I have heard about this before but I am sorry, it sounds and even looks so gross. I bet its super messy too. But that's just me, I am probably in the minority on this one.
Everytime I see one of these, I just imagine all the different squishy textures and soggy pie crust. Granted, the ones I have come across are always 2 or more pies inside a cake, a single one might not be so bad.
I would try it if it was free, and I didn't have to make it, haha.
I will be experimenting with this - a good friend of mine is getting married on 3/14/15 and is running with the pi/pie quirk to the date. She likes the idea of this as their cake for cutting (regular mini pies for everyone else, maybe a cake stashed away for people who ask). The one I saw was pecan pie/spice cake, apple pie/vanilla cake, and pumpkin pie/chocolate (huge pake) and I believe they said that they add an egg to the pie dough to help it hold up.
I'll report how our tests go.
That would be SO rich and heavy...can't imagine taking a bite of it!! Shellebellecake... do tell how it goes!