I am really enjoying WOW so far except for one major thing...
SPAGGRO! This is when a mob spawns on top of you and commences to ripping you a new one! It usually happens when you are in the middle of fighting another mob and I am getting tired of it.
It wont take them much work to fix it, but they better do it soon otherwise they are going to lose alot of players!
Personally I see a MMORPG as an attempt at bringing table-top roleplaying (such as D&D) to the PC. But as long as I can actually see a monster appear from nowhere, MMORPG's will never be anything like a REAL roleplaying game.
They could easily write code that would detect if any players are in the area, and spawn the mobs out of the line of sight from the players and have the mob walk to their position (camp, area of a forest they inhabit). Even if they spawn in another room in a castle, or just over the hill from the players that would be fine.