In Europe you could try quoting the regulations regarding "cool off periods" for purchases. That usually extends to a week, give or take the service involved. SInce the game is not "live" live, you could probably get your money back up to Live. Not the European release date (Feb 5) but the actual universe Live date.
In the States, you've got til midnight the 3rd day of purchase. Then you're boned.
All things considered, we're not even in Live yet. When I last played WoW I was STILL seeing queues primetime on weekends.