I have been running my 4 Rios on an old PC that did not support WOL. I have been leaving the PC on all the time in a very un-ecologically friendly manner, but used the excuse that it was also hosting my internet connection (dial-up: no broadband yet in deepest Kent) so it didn't matter.
Anyhow, I have been upgrading PCs and have been tinkering with a WOL enabled workstation (the SERVER) that hosts the internet connection, is networked to a couple of other PCs and serves the Rios. If the SERVER is sleeping, it can be woken by another networked PC requesting a web page. I therefore think that WOL is working OK.
However, when the SERVER is the only PC on, it will not go into standby mode (S3, or STR) unless the Rios are switched off: if they are either active or in standby mode, they keep the SERVER awake. If I soft-power them off (so the screen is blank), then the SERVER will sleep, but when they are turned back on again they cannot wake the SERVER.

Under the original ARM setup, the SERVER will only go to sleep if the Rio is in "soft off" mode (i.e. blank screen). However, when the Rio power button is pressed to switch it on, the SERVER wakes up as expected.

Anybody else experienced this? What sounds best to me is for the SERVER to be able to sleep when the Rio is in active (but not playing anything) and standby mode, and be woken up on a change from standby to active.
I think Hugo mentioned that a Rio will not wake a PC on an initial power-up due to MAC address issues.

Cheers

Mark