Not similar as in Realms PvP, or... ?
Because I don't see anything they do different than GW2 or even Planetside 2 or Darkfall other than the skin the game comes in. I still think to the vast majority of PvPers (not those on these boards), most people don't give a shit about the mechanical side of any PvP match. Like, they don't know why having more than one entrance on a keep is important and they will happily line up like people waiting for welfare checks on a flight of stairs while getting ROFLAOED by mages.
The biggest thing to most people is "Am I winning?" If they aren't, they will quit. That goes to faction pride more than anything. I always laugh when I see a poll before a new game launches and they say "What side will you roll?" where a couple hundred vote, and then think about all the hundreds of thousand of other people wondering where the 'The Winning Side' option is, because that's what happens after launch.
The problem with mass PvP is the same thing that makes it attractive from the beginning; the prospect of a large battle with 'thousands of players'. In order for it to work, a game must do what Draeg said, built all that right from the start from scratch. And oh yeah... it needs thousands of players. The whole of the game has to be dedicated to it, it cannot half-step. When one side begins to dominate, the losers start bailing or repatriating and then the population gets smaller. Few weeks/months later it repeats, even if the "losing side" now flips to winning.. people who were used to winning start quitting.
Imo, PvP should never be designed for a large scale. It would just cost too much. It should stay as a niche industry where those 300k players will stay because the game gives them what they want, a reason to keep playing even when they are losing, not because they are winning. I'm not talking about 'Everyone's A Winner!" trophies, but some kind of real incentives to keep people in the game when by all rights they should have no reason to stick around because PRX will smash their faces in again.