Not a wowkiller, but could've been.
If you want to just try something else for a while, or maybe WoW never really was your thing, Age of Conan is a viable alternative. It has things it's bigger brother does not. The game itself is a lot more brutal, bloody, and mature. You will see heads on pikes, plenty of blood, breasts, etc. This is not a game for children.
That's another positive aspect to the game. The players themselves are usually more mature. Sure, you will run into immature individuals from time to time, but not to the scale that is WoW tradechat. You usually won't run into the same kind of arrogant individuals that you will find on WoW. No one really touts gearscore or other segregating things on Conan, at least to the extent that WoW does. Mind you, I haven't raided in Conan, so correct me if I am wrong. But so far I have not seen it.
The graphics are also decent, the quests are good and pretty straightforward. The group questing and instancing is also well done. It's also fairly challenging. The only gripes I have with the game is that there is a lot of room for improvement in a lot of areas. Professions could have been done a lot better. Zone questing and transitioning is also confusing and frustrating at times.