A lot of people complain about world PvP. The profanity filter fills chat with interesting @#!$%'s and ^&*!'s when someone’s come out on the losing end of an attack, and I hear the dreadful moans of people when new zones like Zul'Aman open up or events like the Headless Horseman take us deep into Horde territory. There we know they'll be lying in wait, ready to chain-fear-stun-MS-DoT-PoM-Pyro us into oblivion. The odds are heavily against us in such situations, and, yet...
I love it.
Perhaps it's just in my nature to enjoy this clash of uneven proportions. When you go into an instance, you have some idea of what you're facing. You look up the dungeon, you know in general you need a tank and a healer and some dps and cc. You're going to pull some trash, the boss is going to have tricks up his sleeve. Fun, but it can become routine. Everyone knows to interrupt Dalliah’s heals right after she spins; it’s like clockwork. PvP, however, is a surprise. Unless you've memorized every armor graphic in all its colors and uses you can't always tell what you're up against. Is that priest a soon-to-be splatter of holy sparkles or are they going to suddenly turn purple and melt your face? Is this paladin going to be largely ineffectual yet take an hour to burn down or are you going to be hurting from super-buffed holy shocks? ...Is that a rogue in the bushes?
It's not always fair. You can be the ganker or the ganked. You can be in the middle of an epic battle and be sniped from a distance, utterly mutilating your storybook ending. But amazing things can happen as well. You can come across a rare elite, gather some guildies, and find that some Horde are now trying to take it down. You take them out and proceed to go about procuring the elite's pretty blue drop. And then the horde come back and assault your healer in the middle of the battle, and, amazingly, you kill them, all while your tank keeps aggro on the elite and you down that sucker for some nice boots. It's that kind of event that makes you love PvP servers.
Skeletons strewn all over the floor of Scarlet Monastary, outside of Karazhan and piled high on the Arena Vendor give testament to the blood thirst. Uneasy truces outside of the Coilfang instances end when some Hunter looses a single bullet and then no one is summoning, not until one side shows its dominance (generally whichever side has an SSC raid going that day). You learn who to avoid when you’re out by yourself. These are the same people you desperately want to introduce to the dirt someday and also have that tentative Sun Tzu-style respect for at the same time. In a way, you get to know players of the faction much better. I’ve learned the names of several Horde who were content to let me level on my own, even helping me or allowing me to help them. At the same time, I know who not to be caught in the same zone with, and who will spit on my corpse and do a little dance.
It spices up gameplay. How often have you killed that same group of clefthoof bulls? Odds are, more times than you care to remember or that even the most diligent psychoanalyst could dredge up from that wall of mental repression. Now, how often have you killed them while looking over your shoulder for that level 70 feral druid who desperately wants both the bulls and you dead so that he can complete his clefthoof set? It paints a slightly more frantic picture in your mind of quest completion and dodging the reaper. It also prevents the situation in which you need to report the unflagged prancing elf for ganking your quest objects after you unwittingly pulled the mobs away for him time and time again. Upset? Want some retribution? Smack him in the face with your hammer and grab your quest item. Problem solved.
If you have some aversion to dying or "wasting time" I could see how PvP could be annoying. If you don't like the uncertainty of winning or losing, PvP can be a hassle. And yes, ganking generally sucks, as does the fact that Horde primarily control elemental plateau when all you want are the mats for +81 healing to your shiny new mace. But the thrill of the come-from-behind win, the killing blow on the rogue who thought it would be easy to stab you from behind, or making three Horde chase you for over a minute away from the front of Kara all the way past the Vice and almost to the bridge, travel-forming, healing and abolishing poisons the whole way so your guildies can rez and summon your raid to thoroughly slam your pursuers’ faces once they return completely, in my mind, makes up for any bad experience to be found at Nessingwary's.