I play a Shaman as my main, and I've said it more than once to my guild already: as much as I can, I will outright refuse to group with Paladins in the Burning Crusade. I don't care if they are on our side, if they do bring that sweet, sweet Judgement of Wisdom, and if they are really corrupting the light-- a Pally is a Pally. They're my sworn enemy, and that means they have to die (as soon as that shield fades, anyway).
And I'm not alone-- Jingle refuses Blood Elves in general on behalf of the entire Horde. And interfaction discrimination doesn't have to wait until the Burning Crusade-- Julious points out that Gnomes seem to get no respect at all, even from Alliance. Hey, I respect Gnomes plenty. I respect them at dinnertime with a fine Durotar wine, usually after they've been grilled or charbroiled.
So where do you land on all of this? Can't stand the sight of some of your supposed allies (I'll just assume you already hate the other faction), or do you think we should all just get along?