how about "Sleep mode". With my eco-friendly credentials gnawing at my conscience, I struggle to accept using an application that requires the server to be permanently on when WOL is out there and available

The problem is that the servers are also really the client... without the server working the client devices are useless

Am I the only one that cares about this?

Quite possibly

The stock ARM handles this perfectly (thank you Roger) but tRio doesn't, and neither does Medianet. I am not a tecchie, so bear with me, but is it tough to do or is it that no one really wants it?

Speaking for medianet the rio is only one device it supports, the other devices need the server to function in any way. e.g. mvp, slimp3 etc will all start complaining if the server vanishes (then there would be no clock/date function etc etc
Also as medianet does TTS / HA control etc it needs the devices alive and kicking to provide the quickest response possible