So Pet Charms is our new currency. Since I got lots of stacks of treats(from celestial tournament and still lots of tokens to buy more with), bandages(from leveling up all pets to 25 from pandaria trainers) and battle-stones(except I have now run out of flying stones due to the number of new flying pets in WoD) I only spend my Pet Charms on Battle-Training Stones.
This is a double edged thing to do. It really helps to speed up leveling the new pets but on the other hand I get less PvE battles to count against the 500 battles achive.
I guess Pet Charms is a good way for more casual pet-battlers to get treats/bandages/stones, but I would hope that they could add some high-end things to buy with Pet Charms.