i agree with everyone else. since i have a weird work schedule, i do it at 3 or 4 for many reasons, 1) that's when i have the most energy 2) i like to sleep in 3) that's when i'm most likely to snack 4) if it's a cardio day, i can watch those celebrity shows on tv while i run/do the elliptical
5) i'm home in time to miss the after work crowds and in time to make dinner and unwind.
i think it's just whatever works for you. in theory i would love to work out in the morning, but to be honest on days my schedule permits it, i just wouldn't be at peak energy to get in as an effective work out as later in the afternoon.