I tried to buy a 50" ST50 from Amazon because of the Chase 5% MARCH cash back promo for Amazon. Placed my order on Sunday. As of last night it had not shipped yet. You don't get charged until it ships. I would be surprised if you item ships same day as you place your Amazon order (with Super Saver Shipping, like I did).
I ended up cancelling my Amazon order because I didn't think I would get charged in time to use the 5% promo. Would be interested in opinions on AOM. Amazon does have the 30-day price guarantee as well as 30 free return policy that is attractive though. Not sure of AOM's policies.