The patch fixes various multiplayer bugs that would make the player invisible, remove fire arrow damage and cause players to be "de-synced if killed in mid-air." It also adds information about maps and makes more room for map names in the player map lobby. The single player component gets fixes for the leaderboard, a mission's objective display and a bug that made discarded weapons stay on screen
Perhaps the biggest change is in the single player HUD, which received criticism for its clutter and can now be adjusted to taste by turning elements on and off. Earlier this month, Far Cry 3's developers announced that they were working on a patch to customize the PC version's HUD. A representative from Ubisoft told Polygon that the developer hasn't made a decision about bringing HUD customization to consoles.
You can download the patch and check out the full list of changes here.