Like riding a roller coaster, it seems like ordering Nexus devices from the Play Store is full of its ups and downs. Today, it's up! At least, for the 16GB and 32GB Nexus 10 for U.S. customers. The two tablets have just gone back in stock via Google's storefront. There is even an encouraging "Ships in less than one week" disclaimer. Ordering seems to be working flawlessly at the moment, though, there isn't a huge rush right now. Still, if you're looking to get one, this would be a good time.
As you probably already know, the 16GB costs $399 and 32GB costs $499. Customers will be told that they will not be charged until their orders have shipped, however it looks like pending charges may still appear on your account, so be careful if you're planning to order with cards that do not have funds available yet.