A new quest will pop up once your first pet reaches level 3. It will send you to either Audrey Burnhep in Stormwind or Varzok in Orgrimmar. These trainers will offer a quest chain to battle specific Pet Tamer NPCs on each continent. Defeating each of these NPCs will reward a nice chunk of experience for your pets, as well a Sack of Pet Supplies (which has the chance to drop the Porcupette companion, among the always-useful pet bandages).
So far i've done almost half in the past 2 weeks or so. I just want to know would it actually be beneficial to do the above tasks? Just all seems a bit too grindy, I feel like I've been wasting so much time doing old content that's not even needed any more... but I didn't mind doing them for the transmogs and such. I guess i'm just asking if this addon is really worth using and it's not suggesting unneeded filler.