The song should not be in the slow, pounding 4/4 we always sing it in. Or most recently, the faux Gaelic character of dreamy pensiveness. It's Irish, centuries old, and the rhythm should be freer. Before you listen, imagine the hymn you know. Now imagine it quick and light - add an Irish accent - and sung as an air.
This isn't quite it. He takes his time getting to the song and you might skip to 2.54, for openers. Chelsea Moon's version is also good, though too slow and pensive. But this may help break the spell of how we've pulled the song out from its roots. It's one of my favorites anyway. If anyone can do this right, they can sing it at my funeral. (Yes, I hope to tell everyone how they got something not quite right one more time.)