Dunno yet
I'm only level 19 and haven't been into the high traffic PVP areas.
It's got a good quest system to build you up in levels. Seems like PVP starts around the early 20s as the quests send you out into dangerous areas.
Right now I'd get eaten by most critters in the PVP zones.
A character can enter a non-contested zone and explore it, but if he's in your zone, he can't attack you until you attack first. So it makes it very dangerous for explorers checking out enemy zones.
It's down for the next two days though, so I'll have to wait to get into the 20s to see the fighting firsthand.