My priest visited the new open world PvP zone Wintergrasp for the first time at level 76 this weekend, then again at level 77 with a flying mount. Which didn't help much, as it is a no-fly zone. Anyway, besides just running around and getting my mining skill up to 450, I also participated in two keep defense battles there, and one attack. And got a strong reminder how Blizzard is making life so difficult for the competition: They "borrow" the ideas of others, and implement them better. Yeah, I know, I'll get another bunch on anonymous people accusing me of having a hidden agenda to destroy WAR. But Wintergrasp is an excellent version of PvP keep battles.
One major difference between previous versions of keep battles and the WoW version is that in Winterspring you can drive around with catapults and other moving war engines, not just fixed siege engines. And in Wintergrasp the towers and walls of the keep are destructible, not just the doors. There is even a buff for the less numerous side to avoid the outnumbered side being steamrolled! And while of course there is no RvR in WoW, the Wintergrasp keep capture gives a server-wide buff for the winning side, for +5% xp and the opportunity to gather Stone Keeper's Shards, which can then be used as currency to buy various recipes and other stuff. Winning also gives access to a raid instance, and to added monsters in the zone that can be farmed for expensive elemental tradegood drops.
It is totally possible that a keep falls at 3 am to a group of attackers with no defenders in sight. But during the day the battles are better populated: They only happen about every 3 hours, for up to half an hour. If the attacker takes the keep, the battle is over sooner, and you'll have to wait two-and-a-half hours for the next battle. As there is only one keep in the game, the people who want to do keep warfare are all concentrated at this one place, so even in the morning there is enough action in those keep battles. And for those, like me, who aren't big PvPers, the turrets and vehicles allow you to make an impact in the battle, even if you aren't a trained player killer.
World of Warcraft is not a PvP game, and it is unlikely that the addition of Wintergrasp will make a lot of people quit their more PvP-centric games to play WoW instead. But for those of us who just want a fun keep battle once in a while, with good rewards and some varied gameplay, Wintergrasp is a lot of fun. You can find a detailed description of the rules at Moonfire, and a discussion of the incentives over at Player versus Developer.
Of course you could argue that Wintergrasp is as unoriginal as a fake Rolex. But if you could get a fake Rolex with more features which actually looked better and ran better than the original, how much would originality be worth to you?