While the Golden Sun music is a masterpiece, and I am a major fan of the series... I will review this with great caution and reservation.
This OST loses severe points as the quality of the music is very low. More specifically, this is a game rip. For most, hearing the GBA pumping out music is enough, but I'd rather listen to 192kbps-320kbps arranged pieces. Now the problem with these rips are that they are done POORLY. The music is cut off abruptly, and you can hear bits of the song looping back to the beginning before it is cut off on several pieces. If the timing was done right, it'd be fine... Or at least if fade outs were introduced.
Overall, this deserves a big fat 6. It's great to hear the music, but there's definitely huge room for improvement to disguise the fact that it's a rip.