I use the ATV pretty much every day when I get home from work, so now I set my 'server' Mac to boot up automatically around 7pm on weekdays, and iTunes is set to launch on login. It's set to auto-shutdown in the early hours of the morning too.
It's not as energy-efficient as a (functional) wake-on-access feature, but it works ok for me.
I've resorted to doing the same with my MBP. Well, almost the same. I set my MBP to wake at 6pm and sleep at midnight. I would vastly prefer the wake on network access function over this option, but this works in the meantime.