Up at 0420, workout, breakfast and start work at around 0600-0630. I really value the early morning time for clearing my head, working on key projects etc. I'm very productive early in the AM and it's some of my best time. Because of the crazy awake time I do go to bed between 9-9:30 every evening. Staying up much beyond 10:30 will pretty much render me useless the next day!
The above noted, I recently listened to an HBR podcast and one of the discussions was on people who are naturally wired to get up early and those who were later risers. I definitely think that trying to force something that is not natural is not always a good thing. Give it a shot for a few months and see what happens!
Did you find that it took time to get used to getting up at 420 and do you feel "awake" - full or energy etc or sleepy..does it take a while to get going?