This morning, Microsoft posted that it was accepting new users into the Xbox Live dashboard preview. This afternoon ... not so much (transition pictured).
After seeing the post this morning, we contacted the company to get specifics, as the registration wasn't working properly. Since then, Microsoft has altered the text and sent us the following statement: "Unfortunately we don't have any details to share at this time."
We'll take this as a case of "switch flipped too early."