@meleu
I have one of their v1 boards when it was called game pi advance. Here my build log.
Gba worked well (can't remember the core off the top of my head) but if your wanting gba achievements, it didn't run mGBA very well. There new free play CM3 board with the built in pi 3 sounds really impressive.
I also have a Gameboy Zero which uses an original DMG-01 shell, with X and Y added to the front and L and R added to the back. Sudomod.com I'm currently upgrading mine to a raspberry pi z w and New hdmi screen.
The weirdest thing is that the GameBoy Zero run mGba very well but the game pie advance didn't, same pi, same retroarch version, same core version.