Here is basically my experience with PVP.
You're just minding your own business fighting mobs and suddenly you're dead backstabbed by some rogue you couldn't see.
You're running around looking for someone to PVP and you attack a player that's minding their own business fighting mobs and suddenly they're dead, backstabbed by some rogue they didn't see.
You're trying to do a raid event (before all this instanced stuff) and lead guild on the server shows up, trains you "on accident" wipes your entire raid every time you try to do the content.
You're checking out the raid event you want to do when you realize the guild under you in progression is about to engage in the content, so you train them "on accident" wiping their entire raid every time they try to do the content.
What's PVP like now? Probably not much different, just a much lower population on the servers.
Arena is about the only way you can get close to fighting another player without the expectation for NPC's getting involved in the fight. You're probably going to get jumped because fighting fair is for friends. If you do happen to win, "Just wait till I log my main!"