I'm slowly transitioning myself into working early morning to allow for later meetings at work, and it is seriously tough to get into. It's involving a complete change in schedule and routine. Everything I've read points to a morning workout being more beneficial in more ways than one. Working out in the morning gets your metabolism up for the day..burn more calories, more energetic, it sets the tone and gives you positive energy throughout the day (provided you get to the gym early enough).
I've also heard a lot of people say that it doesn't matter either way, it's a scheduling thing. But if it matters when you eat, when you sleep, what you drink, and the order of the machines and workout you do...it logically matters what time you work out too. But again...it's tough - it ends up feeling like 10pm at 6 kinda thing. So worth it/not worth it?