I gave up and called Trachtenberg this morning. The email is, in fact, an unofficial acceptance letter. They like to work fast, the woman at the school said. Statuses will be updated online sometime in the next few days. I checked my application and turns out that I applied on the 14th, and I hadn't believed that it was possible for them to make decisions that quickly. So, we're really in (unofficially), Application_Overwhelmed!