If anyone wants the 512 GB version of Surface Pro 2, it is listed at the moment (11/8/13 @ 10:00 AM MST) as in stock and available for shipping on Best Buy's web site.
The Microsoft Store in Houston, TX also called a couple of days ago to let me know they received two of the 512GB units in stock. When I went there today, they also had two of the 256GB units in stock (lucky me). Guess they're still trickling at various places...