Okay, but what is each tree good for?
It looks as if Blizzard intended each tree to have a different playstyle focus. Tenacity looks pretty strong for soloing or using a pet as a tank in a small group. Ferocity looks pretty strong for raiding and straight-out DPS. And Cunning, according to the pet trainer dialog currently in game, is good for Arenas and Battlegrounds. Reports from actual players, however, indicate that all three trees are going to be powerful companions for most purposes.
