I just got an acceptance letter from Berkeley for the Earth and Planetary Sciences Ph.D. program. The letter says that detailed financial support information "will be sent separately," but the letter is official. During a recent visit to Caltech, I was told that I should expect an acceptance letter in the next couple weeks from the ESE program. (I'm in Atmospheric Chem, which is housed in different departments depending on the university.)
Furthermore, a professor at Harvard emailed me this morning to say that I was accepted, provided information about the stipend and an additional fellowship I was awarded, mentioned research and class start dates, and offered to schedule my visit. That's not a notice on official letterhead from the dean's office, but it's official enough for my taste.