If people would actually roleplay, and only kill people when they have a reason for it, I would enjoy PvP, however it isn\'t like that. Griefers start hunting people instead of monsters, only to be a pain in the rear for everyone else, and that\'s why I never have supported PvP in any way. Of course, if you had the chance of getting your character removed permanently from the game, for being caught after killing someone, I\'d like it, however if not, it\'s just a question about time before the PKers start ruining the game for others. Personally, I think it does not matter at all, whether only some parts of the world has PvP enabled, or if it\'s the whole world. It\'s the fact that people misuse the PvP concept to get rid of people who they think are not k00l enough.
So, if there\'s a very strong consequence for killing someone, reason or no reason, I\'m in for it. Otherwise, I\'d say keep it to pre-arranged duels and arenas.
Besides, it\'s impossible to RolePlay PvP in a MMORPG, as there simply are too many people who don\'t do it, and it kindof spoils the RolePlay element.