Myself and a number of my guildies all bought War, about 50% have dropped it and the rest of us have subscribed. As another poster said it's a completely different game in a lot of respects with a different appeal to players. Personally I'd prefer not to PvP in BG's/Arenas in WoW - I'm not terribly good at it for one thing and, perhaps as a consequence, I don't find it very interesting or engaging. War on the other hand, I can't get enough of PvP and all I can do is think that collision is the difference. PvP when a line of 'tanks' can actually block melee from getting to your ranged if they find a choke point is completely new to me and I love it - it allows for defensive formations, sneaky tricks and lots more. Even playing a healer (something like 8 chars in the 11-25 range atm) you have a definite sense of your worth as a good healer on one side can completely change the balance of a battle (and people will whisper you thanks for your efforts!).

As other people are saying, I'll stick with WoW for my PvE but War is, for me, my PvP home.