Yes, surprise surprise: PvP works well when it's PvP. Wow, look at this PvP! It's really PvP!!! Whoohoo. Holy grail what a revelation this is. No one ever knew this! I don't know, but I play games for some 30 years now. Back then we used to hotseat but this concept isn't really new.It works pretty well in powerplay, from my couple of years' experience, even with normal limitations around instancing. But only if both sides are in open, exposed to the same risks, otherwise it's pretty limp and leads to bad feeling between sides.
Still doesn't work with PvE players.