Apple started pre-orders for the iPad Mini at 3AM ET. It's already outta initial stock of White iPad Minis, with shipping times having now slipped by 2 weeks from the original "Delivers 11/2" promise. The black Wi-Fi iPad mini remains available for delivery by November 2nd. For now.
It's tough to say whether the white iPad selling out so fast is down to high demand or low supply. Some other countries have been listing the 2 week wait from the off, though, which suggests that Apple isn't sitting on as much stock as it would like.