I've done both - spent time working early mornings and also into the night. I found that working early in the morning I'm more productive per hour than I am at night. I find nighttime working to be more creative though. The mornings are good for me "getting things done" and by 9-10am all the planned work I had was done
My experience mirrors this. I get through a lot more work and admin in a given day if I work from 7am-4pm, especially if there's a lot of drudgery involved. In contrast, if I work from 9am-6pm or later I'm more likely to procrastinate but I get a spurt of creativity that starts in the late afternoon and gets amplified at night. So I try to structure my work day around that, using early mornings to race through necessary but boring work and to tie up the remaining loose ends from the day or night before while leaving particularly challenging problems for later in the day or the evening. Not to mention that the feeling of getting a bunch of tasks out of your way early in the morning usually acts as a potent motivator for the rest of the day.
I'm not sure if it's a product of it being quieter in the early morning when I first wake up (as opposed to at noon), the fact that recently I've been alone in the "office" for most of the day, or what, but I definitely find it easier to get into "the zone" in the morning and get a lot of work done.
I'm writing code 8-12 hours a day now, which is pretty outstanding considering it isn't a new project or something. The fact that I'm exhausted by about 8pm doesn't really bother me.
I'm not a morning person, but my experience is similar to yours. What I settled on when circumstances allow for it is to wake up early in the morning to get non-creative stuff done. Then, I have a nap for maybe 2 hours. Following this nap, I continue on with my day, first taking care of the new work generated by my first round of morning work, before settling in on the meat of what I do when most people are winding up for the day.
