It's an interesting moment, the one that mikkeneko talks about over on WoW LJ. It's the one where you first enter a battleground, or an Arena, or just head out into the world, attack someone of the opposite faction and win, and first realize that yes, you can PvP.
I come, like many more experienced gamers, from a Counterstrike background (and a Doom and Quake background before that), so I've almost always known the thrill of taking on other humans at their own computers. But this moment happened for me before I ever played WoW -- back in the days of Dark Age of Camelot, I entered a battleground, saw nameless player opponents in front of me flagged red, actually killed one, and realized that yes, I could actually do this. Our own Dan O'Halloran just recently had this experience in WoW, I believe -- he told us on the podcast a little while back that he'd never played PvP, and a week or so later, he told me he'd tried out a battleground and learned it was actually a lot of fun.
PvP isn't hard -- you mostly play the character as you play it in PvE, and as fast as high-end Arena matches can get, battlegrounds especially are simple enough for even casual players to enter and at least partly influence the battle. I don't remember what's so scary about PvP but I do remember it being scary way back when. If you haven't played PvP yet, though, you're missing out -- jump into a battleground, throw some spells or swords around, and you'll find that you too can PvP.