The iPad mini was not the only iPad to sell out this week. By Tuesday, Apple's pre-order inventory of the fourth generation iPad had also sold out, with the website giving a shipping time of one week. AppleInsider has posted a summary of the early reviews, which generally recognize that this is an incremental upgrade. Testing by CNET confirms that the iPad is indeed twice as fast as the third generation iPad with retina display, as well as being faster than the iPhone 5. In addition to speed, the reviews praised the improvement in the FaceTime camera, and they noted the new Lightning connector.
Regarding the iPad mini, according to AppleInsider, a market analyst is predicing that Apple will sell 1.5 million iPad minis over the launch weekend, Nov. 2-4. That would compare with the 3 million iPads with retina display sold when that product launched in March. It's possible that the mini's launch would have been larger if the models with cellular connective had been available at launch. Apple only reports the actual number sold, not the number ordered.