I also attempted to have WhileIdle run as a serivice to see if I could have it kick in if no users were logged in. (E.g. Windows updates @ 3am auto restarting the machine)
I was able to have it run as a serivice and activate poclbm, but it kicked in instantly (didnt want the 10 mins) and it was using the CPU as the openCL Device instead of the ATI card. It also did not seem responsive to mouse movements, it kept running instead of killing the process.
My dream would be a hidden, run as a service, remote reporting & managable bitcoin client that also had extra goodies built in like automatic memory clock frequency changing, thermal limits, fan speed controls, time of day settings, etc.
Running as a service is one thing, but a miner won't be able to work on Windows unless someone is physically logged in. Windows does not allocate the video card drivers until someone does. This is why miners only see the CPU available. The same is true if you RDP into a machine and try to mine as well.