In certain ways, playing a hunter is about depletion. You have to worry about running out of ammo, running out of mana (although not as much since Aspect of the Viper was introduced), running out of range to fire your weapon (though thankfully there's no longer a dead zone), and of course you have to worry about your pet running out of happiness. Which means we have to carry around stacks of food in our bag space, which let's not forget is one bag smaller because every hunter needs an ammo bag, and often some extra ammo on top of that. For some reason, I've never thought about this before: why do we need happiness at all?
Sure, it's a nice mechanic at first, adds flavor to the class, but I really like this suggestion by Killernuts (*cough*) of Arthas-H: remove happiness once your pet reaches the top loyalty level. After a while it just becomes a pain; at best I click an AddOn button every once in a while when the alert pops up, and at worst I have to take a break from what I'm doing to scrounge up some food. Or instead of removing it based on pet level, how about based on player level? Make a trainable skill at, say, 30 that keeps pets happy. You can use food to boost their happiness faster (useful with a newly-trained pet), but you don't have to.
At least one nice change is already slated for the pet feeding department: pets will be able to be fed in combat "at some point in a future patch" (Nethaera). So I guess that's nice, since indeed it does suck to lose what can be a significant portion of your damage just because you haven't been obsessively monitoring that little smiley face. Prior to 2.3 it was possible to feign death and then feed one's pet, but this has been "fixed".