Well, as a Hunter, I can't really see much of a PvP change from this. If you guys want to go after my pet, he will pretty much stay still until I give him a new order. If you are chasing me, he will be chewing your ***** Same as before, really.
This "buff" was made primarily to help Hunters in raids, because sicking a pet on certain bosses was just a very very stupid thing to do. Now they might actually survive long enough to do what they were intended to do all along. Provide a DoT on the target, and give the Ferocious Inspiration buff to the group if you were BM.
Besides, I'd think you guys were happy when you could finally Stealth/Vanish without our pet popping you guys back out quite so often. And to be honest, that was a "bug" I fervently wished to have removed myself. Nice in the odd PvP encounter, but it removed alot of the challenge I crave in PvP.