This board is of exceptional quality and is the only one I've seen that breaks out the address lines in such an orderly way.
It's been working perfectly to allow me to to prototype my own cartridge design. The seller was super responsive to my needs and sent them immediatly and with reasonable shipping.
I only wish I had put 90 degree headers on it, probably mounted on the back(as the pins are labelled) for my purposes and I'm thinking of desoldering the headers to do just that. Make sure you don't solder the headers on before you figure out how your are going to mount your gameboy near your breadboard.
If I need more and they are in stock, I know I'm coming right back.