An American names his talk "What I wish I would have known about X before Y" (slightly surprising to me, who would have expected "What I wish I had known..."):
A page from an English-as-a-foreign-language grammar here says that that the would with I wish expresses a desire for things to change in the future, not for things to have turned out to be different. In the case of this title though, it's clearly a desire for things to have been different by point Y.
