From what I've played of it and what I've seen online, it seems like a pretty awesome game, kind of like Zelda 1 mixed with an action/platformer. It also is EXTREMELY difficult. I don't see how anyone could finish it without either a manual or a lot of hints. Or both.
It was also the direct inspiration for an indie game by the name of La-Mulana, which is also good, but possibly even HARDER. If you like Galious, give this one a try.