Hi,
For me, it depends on the kind of workout I'm going to do. If I'm going to do my "run/walk" I like to be "empty" but hydrated. Any time I'm going to do an impact workout, not eating beforehand is most comfortable for me. If I'm going to do a workout like Muscle Endurance or any of the strength DVDs, I'll eat something light, like a banana or yogurt.
As far as the time of workouts...I can't seem to do the really hard ones like Kick Punch and Crunch early in the morning. In the winter I tend to do a short, not so intense routine in the morning (such as Push Pull) and after work I'll do a more thorough session with High Step or the Pyramids.