KT- you into past mmorpgs? WOW is a bit different, it fills a distinct niche in genre that I think everyone that played EQ or whatever has been waiting for.
EQ was a serious grind: kill things, lvl up, kill bigger things, repeat. It was focused on grouping with other players and working together. WoW is about exploring the world, doing as many different things as possible. It seems to have been designed specifically to remove the grind part. It's basically taken the mmorpg formula and simpled it down. Once in a while I miss the class interaction from games like EQ where you needed to balance your groups to win, but WOW makes up for it in other ways, like having a huge world to explore and not having to devote ungodly amounts of time to succeed.
I'ts not a serious, in depth game. Quests are usually simple, playing your class well doesnt take a lot of practice- though certain ones like the rogue are very customizable, other basic ones like the mage will be mostly the same for everyone. If you're into other mmorpg, this will either feel like a vacation and be a blast or be far too simple and bore you silly. If you're into more hardcore rpg's like Morrowind, skip this. If you're into complex interaction with other people, also skip this- you'll do a lot alone or in small groups until very late in the game as quests gradually get harder. If you're really into the Warcraft story and world, this will be great.
In short, know what you're getting into and enjoy the games strengths and you'll have a blast, aim too high and you're going to miss.