Reports of DST-related malfunctions vary wildly, with some iPhone and iPod touch alarms going off early, some late, and with some working just fine. Crazily, one iPhone 3GS user says that his phone correctly jumped forward an hour on Sunday night, but then reverted back an hour yesterday, causing him to be late for work. It's unlikely that these DST issues are caused by a simple bug, either: one iPhone user in Arizona, the only mainland U.S. state that doesn't observe DST, says that his iPhone still automatically jumped forward an hour.
There is currently no known solution. Engadget is reporting on a wide range of possibles fixes -- from a simple restart, to calling your iPhone from another phone -- but as we don't know the underlying cause, it's unlikely that an exact fix exists. It might be variation between devices running iOS 4.2 and 4.3, for example, and perhaps jailbroken iOS devices act differently too. We'll update this post as we learn more. For the time being, make sure the time shown on your phone is correct!