God that was painful :-). I lost a lot of time in WoW, perhaps it was an escape, but I spent hours learning the various nooks and crannies, leveling up over 3 dozen characters of various types to the max level. I had people I never met that I felt were good friends, shared battles and triumphs and failures. Laughed at the sometimes incredibly subtle in game humor, and sometimes not so subtle. Collected odd recipes to cook, outfits to wear, and trophies and achievements. I loved having the 'two ring' which was one better than the One Ring.

But as others point out, the 'traditional' way to build an MMO is 'learn skills by levelling up / start playing at max level' The game set a number of challenges for 'max level' characters which depended on gear, group composition, and various strategies to overcome the game mechanics. That is where it failed for me.

In WoW while leveling you often needed to join up with groups to run through a local dungeon together. It was fun when you had a good group, annoying when you had children in the group. There were too many ways for 10 - 12 yr old boys to grief people.

In an effort to increase its appeal, Blizzard changed it again and again. Skill changes, techniques, complexity was removed, buffs and nerfs to various skills. Lots of change and slowly less and less appeal. All of the components were there to make it better (arenas were a great testing ground for devs to evaluate PvP changes).

I stopped playing when Mists shipped. It was just too stupid at that point and the similarity to kung-fu panda to stark. Oddly, if you could provide servers that stopped at one of the expansions (Wrath or maybe even Cataclysm) I would still be spending money with Blizzard, but now not so much.

I look at it periodically and see the makings of a durable world/gaming simulation environment. I hope someone picks up the challenge.