Remember when iPhones with Flappy Bird installed were going for $600 on EBay. When compared to that this is a bargain. All the classic fun of Flappy Bird bit with the addition of BUTTONS! Gameplay is the exact type that works really well on the Gameboy. Pop it in, thinking you'll play a few rounds and suddenly you've spent 3 hours on the toilet. The cartridge is very high quality and has a wonderful label that looks nice on display when it isn't inside your Gameboy. I wish it had a bit of background music while playing but can't remember if the original did or not.
TLDR: Great Port, lots of fun, buy it.