So, I guess I am. I already have two 60's - a Priest and a Mage. The Priest is in pre-raid BiS, the Mage is on its way there. And I'm leveling a Hunter who is 34 so far.
I don't even know what it is, but I've been playing so much since release that I don't even know if I'm having fun anymore. It feels more like a habit than anything else. I haven't been bored once so far and I could probably level all classes to 60 and get their BiS without ever feeling even slightly bored. I don't care about raiding, but I can just play the rest of the game 16 hours a day and don't even feel the urge to do anything else.
I guess I'm addicted to Classic. How about you?