Unreliability is literally the most noted descriptor of the 2013. No other computer I've ever herd of, treats its major components as consumables, the way the 2013 treats its GPUs. It's perhaps second only to the butterfly keyboard in the list of "greatest Apple hardware screwups" (and I'm including those first-gen PowerPC Powerbooks).
Eh, if anything the 2013 GPUs can't that big a screwup that just because the number of units it must have sold pales in comparison to more mainstream hardware screwups across their Mac and iOS lines.