Why don't you guys just power the machines off when you don't need them? I know some people strongly believe that it's better to have a machine on 24/7 and not risk the shock of initial power-up, so maybe that's your reason.
I second (or third) the request for power management.
The problem with turning the machine off is that it takes such a long time for the boot process to complete when you turn it back on. With two 120+ GB drives in my box, it takes nearly an hour for the file checks to run at startup. That's quite an incentive to keep the box running.
UPDATE: I guess the long startup is just with new disks. I had been putting disks in one at a time as I fiddled with the setup. So, for a while it appeared to take a long time to start each time I did so. This last time, however, I didn't add any new disks, rebooted, and it started right up. Still, power management would be nice to have -- along with wireless and usb support.