Inconsequenti-AL said:
I wonder what sort of basic personality it would have. i.e. Dog = friendly, Cat = aloof, Giant Dire Vulture = ?
Opportunistic. It may be that it doesn't have a friendly attachment to the paladin. They simply have a mutually beneficial relationship; the bird provides the paladin with transportation and a helping talon and in return the bird gets all the rotting flesh it can eat. The longer it goes without getting a meal the more distracted it probably gets. It could just as easily become more focused on getting into the next fight so it can feast, though. *shrug* Obviously it will be happiest when it is eating, and most cooperative when the meat is being
delivered on a regular basis.
This might suit the paladin just fine, a relationship with such easily quantifiable boundaries and rules strikes me as very lawful.

Cheaper than oats too.
In my mind a paladin that would enlist the aid of a giant carrion-eating bird would be a pretty grim character; a follower of his own personal code, his own ideals, not necessarily the ideals of a patron deity. A Dirty Harry type almost. He takes no joy in what he's doing, he just does it and moves on because it's RIGHT and someone has to do right.
I can imagine a necromancer's jaw dropping as he sees the paladin swoop in, lance a zombie and leap off his mount's back. While he starts slashing at the next undead combatant the giant vulture begins making ugly swallowing noises as it tears apart and messily devours the first casualty...
Of course one could play it for comedic effect as well, with the squeaky clean paladin being constantly unnerved and embarrassed by his feathered companion's horrendous choice of food and disgusting manners. There he is trying to comfort the would-be victims of an undead attack while his mount chokes down chunks of the, once walking, corpses.