I really like the world PvP, the adrenalin that kicks in when you see a group of enemy players and you have to choose to fight or run/avoid them, the possibility to invade the enemy factions castles or cities also.
BUT there must be a restriction so the max level players won't be able to gank low-level players. Maybe players from enemy factions can fight if they have max 10lvl difference everything above that is restricted.
And we must have the option to duel one other, to show off some skills if you know what I mean.
Also, it's more interactive to actually travel to the Arena and fight there and not just click on an NPC and teleport there.