As you know by now, because you read every word I post, Apple's iPad MRD is officially for sale on the online, Apple Store. We now have more details about the availability. Here is snippet of the press release from Apple:
iPad mini with Retina display is available to order through the Apple Online Store (www.apple.com) to ship or through Personal Pickup at Apple’s retail stores, and through AT&T, Sprint, T-Mobile, Verizon Wireless and select Apple Authorized Resellers.
You can pick up your MRD at the Apple Store, but only after you have bought and paid for it online, using their Personal Pickup service. It is a good service. That is how I bought my iPad Air. That means that Apple Stores have the MRD, but are not selling them to walk-in customers looking to buy one.
This would be less confusing if it were not for the fact that you can apparently pick up a cellular version at the Big 4 carriers. There are even resellers who will have some for walk-ins. I just read a post suggesting that Best Buy will have them today. I would be surprised if Best Buy had an exclusive. So, it seems the only place you can't walk in a pick up an MRD is the Apple Store. Your best bet is to call your nearest retailer when they open, to see if they have any available.