Rulings
If Guan Yu, Sainted Warrior is removed from the graveyard after the ability triggers but before it resolves, it won't get shuffled into your library.
(wotc • 2009-10-01)
Despite the similarities between horsemanship and flying, horsemanship doesn't interact with flying or reach.
(wotc • 2009-10-01)
If a replacement effect has Guan Yu move to a different zone instead of being put into the graveyard, the ability won't trigger at all.
(wotc • 2009-10-01)
Rulings
If Guan Yu, Sainted Warrior is removed from the graveyard after the ability triggers but before it resolves, it won't get shuffled into your library.
(wotc • 2009-10-01)
Despite the similarities between horsemanship and flying, horsemanship doesn't interact with flying or reach.
(wotc • 2009-10-01)
If a replacement effect has Guan Yu move to a different zone instead of being put into the graveyard, the ability won't trigger at all.
(wotc • 2009-10-01)