One of our Australian forum members, TrAJik let us know that his iPhone alarm failed to wake him up this morning, January 1, 2011 (Australia time) and doing a quick look around the web it seems like he is not alone.
The iPhone had trouble with repeating alarms back during the change to Standard Time so this could be the same bug rearing its ugly head again.
UPDATE: According to comments below, this affects **ONE TIME ALARMS* rather than recurring ones, so the opposite fix should work: