I've actually had the opposite experience: I am waking up earlier, without an alarm clock. I'm not sure I have a good explanation for why, but overall I guess I just feel more rested and have been able to maintain more consistency in my schedule. Less socializing on weekends (which means no late nights) helps too (although I do miss some of it)

As an aside, I've always said I'll know I've made it when I no longer have to wake up to an alarm clock. This is not the scenario I quite had in mind, but I'll take it.