Several outlets are reporting that the iPad mini with Retina display is available for walk-in purchases at a few Apple retail locations. Up until now, the second-generation tablet was only available through Apple.com, with the option to have it shipped to the nearest Apple store for in-store pickup.
Apple has since removed any mention of Personal Pickup from its iPad page, and the new device has been spotted for sale at a number of New York City stores. However, supply is still very limited, and you should order now if you plan to receive an iPad mini before the holidays... Especially if want a cellular model.
The LTE iPad mini is still unavailable through most U.S. carriers, and it is currently listed as shipping in 5-10 business days on Apple's online store. Even with Apple closely monitoring its stock, shipping times could easily slip as the holiday shopping season gets closer.
It is unknown if all Apple stores have the new iPad mini in stock, and it is safe to assume most won't have every model and color. So make sure you call ahead before you make any trips to your local Apple Store.