I never pre-order products because I like to walk in with my money and walk out with my product. I did pre-order the WiFi iPad because I figured it would be hard to get if not pre-ordered.
I'm irritated right now that the week of launch after I pre-ordered Apple comes out with the fact that you will be able to walk right into Best Buy stores in most cities and walk out with the iPad.
The devices will be in stores at 9am, though exactly how many will be available is unknown. I guess that's what I get for pre-ordering something. I've had to put up with Apple's card processor changing the amount they were taking from my bank account for weeks now, it's driving me crazy.