I was in the same boat as you last weekend. Went to order and they were out of stock. Emailed them, but it was the weekend, so I didn't hear back. I checked the page again on Monday and they had them in stock, so I placed my order. Got it yesterday and it's awesome!
Not absolutely sure, but I think I've read somewhere on here that they only put enough units in stock in the store so that they can meet the day-to-day shipping demands. Once they've sold what they can ship the next day or so, they're out until the next day. (If I'm wrong about that, sorry, but I think they were doing it that way at one point.)