Most days I work from 1pm to 9pm here in Spain, which translates to 6am to 2pm Chicago time. That gives me all the time before lunch to enjoy the light of day and all the activities that encourages. I find myself more interested in working out, more eager to read books, and generally infused with more energy for both physical and mental activities.
Over the past few years my average sleep schedule has been roughly 10 PM – 6 AM. When you compare that with a midnight to 8 AM sleep schedule, which is similar to what I was on previously, there are really only four hours of my day that are different: 6 AM – 8 AM and 10 PM – midnight. I’m essentially trading a two hour block at night for a two hour block in the morning.
Occasional I slip back in to a later schedule, whether it’s because of work or social life or I’m just being lazy and sleeping later. When this happens I notice that I don’t like how I spend those hours in question and inevitably force myself back on to the early riser schedule.
Similar to @DHH, I tend to spend those additional two hours in the morning reading, working out, or getting ahead on work for the day. I also enjoy the peacefulness associated with knowing that everyone else is sleeping (and therefore won’t be interrupting me). Comparatively I seem to spend those two hours at night watching TV or playing Xbox. Not that I don’t enjoy those things, but ultimately I’m a much happier person when I’m doing more of the former and less of the latter.