It's a good atmospheric setting, but very tightly scoped. For example, you couldn't use it for a general medieval campaign, but you could use it for a group of warrior-monks or wizard-monks fighting demonic/heretical/evil opponents.
It would fit in well with Merrie England, Stupor Mundi, Crusaders of the Amber Coast or Val-de-Loupe, to give an extra dimension to a medieval setting.
As for Dark Ages S&S, it isn't really Dark Ages at all, but might work for certain types of S&S.