If I'm writing, I'm up around 4:45 and working by 5. I get SOOOOOOOO much more done at that time of the morning, and then I can justify a couple of hours nap after lunch. As long as I get a nap, I'm actually better in the evenings than I am with a later start and no nap.
That said, my body isn't impressed by getting up at that time of the morning, even with afternoon naps and early nights, so I couldn't keep it up year round. I get my best sleep between about 4 and 7, so the rest of the year it's more like 6-6:30 start.