I think it really boils down to personal preference.

I hate exercising on an empty stomach, so I simply don't do it. If I exercise in the morning, I usually have a 100-200 calorie breakfast and then something around 100-200 calories after I exercise (if I happen to be lifting). I'm always starving after I lift heavy :)

i can exercise on an empty stomach in the morning but i like, mentally, to know that i have something in me first...usually it's something small like a protein shake or a couple spoons of peanut butter