I'm sure that there are plenty of people who have gotten informal letters of admission from potential advisers, but who are desperately waiting for the official confirmation of that to come by snail mail. For those who have gone through this process earlier, or have knowledge of it, how long do the official letters take to arrive after the informal e-mails? Also, is the departmental letter considered "official," or is that only the case for the whole package that the Graduate Studies Office sends? For places like Princeton and Harvard, which do not seem to have an online notification system, how do admitted students go about accepting/rejecting the offer? Through e-mail? Other ways?
Any insightful details about this mysterious process would be much appreciated. And yes, you are also free to let the steam off and tell all on the forum just how nervous the time between the informal and formal notifications has been for all of you (who were lucky to be admitted into your respective programs)...I, for one, have not slept properly since being hit with the H-Bomb...