Any feature in a modern MMORPG has a long pedigree, often dating back a decade ago to Everquest and Ultima Online, or even earlier to MUDs and Dungeon & Dragons. That makes the discussion of whether WAR copied features from WoW or the other way round pretty much futile. In Wrath of the Lich King new features are going to be added to World of Warcraft: siege warfare PvP and an achievement system for example. As chances are high that WotLK and WAR will be released around the same time, some people suspect that Blizzard is trying to preempt a possible success of WAR by nicking some of its features. But of course the achievement system could as easily have been copied from Lord of the Rings Online. Who knows? Who is copying whom isn't important. But what is evident is that we are moving towards a situation where the feature lists of all major MMORPGs will look pretty much alike. Now is that a good thing or a bad thing?
As I mentioned before, I don't think that feature lists are all that important. The implementation, and how the features interact with each other are far more vital. For example siege warfare in WoW is going to be strictly localized to one single PvP zone, just a fun diversion. In WAR keeps are far more essential to the RvR gameplay, as they give bonuses to zone control, and thus ultimately the sacking of the enemy capital. In Age of Conan siege warfare is mainly used to crash your computer. ;)
So for me it is always interesting how the various games implement the same feature. Player housing for example was a very different beast in Ultima Online than it is in Everquest 2, which again is much different from player housing in Lord of the Rings Online. I would actually *want* Blizzard to copy that feature, just to see their version of it. If a new game comes out with a feature that is fun, why should everyone be forced to play that game to enjoy that feature. Maybe the new game is otherwise not so great, and you'd rather have that shiny new feature in your old favorite game. Even if innovation is conceived at one point, we're all better off if the best features turn into industry standards. That doesn't turn all games into identical clones, because their basic structure and focus is often different. I'm looking forward to the WoW achievement system, even if it isn't a new idea.