You may find that you simply need less sleep as an early riser.
The benefit is that you become exposed to sunlight at the right times. Even if you mostly stay indoors most of the time, there are several occasions where the bright light enters -- while you're driving a car, when windows are open, etc.
Sunlight has such a strong resetting effect on your circadian rhythm that sleep becomes more efficient when you tend to sleep only when the sun is down.
The strength of this effect depends on your personal photosensitivity. Generally, however, those who tend to live by artificial light and sleep by light (LEDs in the room, sunlight seeping in from the window, etc) -- these people can eventually "flatten" their circadian rhythm and experience a lighter sleep and less vitality during the day. But then again these people tend to drink lots of caffeine so they probably don't notice
