I wouldn't play it if I was you, it will consume your life.
I'm living proof, played since day 1, and amassed 11 level 70 characters (one of each class, two shamans). 4 years of playing, 4 accounts (2 main accounts, 1 account for my kids, and 1 for my old guild bank from when there wasn't an in-game guild banking system). All-in-all, I've spent over 2,000 bucks JUST in monthly fees, not to mention the cost of my 4 original wow copies, 2x Collector's Edition Burning Crusade copies, and 2 regular Burning Crusade Copies. I have over 500 days played totaled on all my characters on all my accounts.
I used to lead the #2 raiding guild on Icecrown for over 2 years, hardcore raiding 6 days a week, over 8 hours a day (I'm a stay-at-home dad

). The past 2 years I've shirked the responibility of running a guild, and retired to a more casual style of raiding, but about 6 months ago, I decided to stop playing for a while.
Although I've made some life-long friends in my time on wow, and I'll probably reactivate at least one of my accounts when the new expansion comes out.
World of Warcraft is not a casual-gamer friendly game, if you play on a PVP server, you're going to get your rear handed to you consistently by the people who have the time to dedicate to get the awesome high level gear, and on PVE servers, you won't get very far in groups using random crap items you find in the game. You pretty much HAVE to dedicate a large chunk of time to gearing your character(s) up in order to be decent at the game. After all, we all know Gear > skill...
Some would argue that if you are a good player you can beat decked-out players, but in all honesty, it's a little hard when they have 13K+ life, and all you can eak out is 7K. It's really just a numbers game.