I am having the same issues with my new 27" iMac (w/BT keyboard, mouse, and Trackpad). It does one of the following two things:
1. Simply won't wake up, regardless of type of input (even wired keyboard). If it's in this state, it also will not wakeup using a scheduled "start or wake" schedule. It must be rebooted using the power button.
2. It will wake, but will fail to light the LED screen. I can control the Mac using the BT keyboard (volume controls, stop/start music, etc.) but the screen will not illuminate. It must be rebooted using the power button.
I've already had two calls with Apple. They've already had me reset PRAM and the SMC. They say the next step is to reinstall the OS. From many in this thread, it sounds like there's some backlighting circuitry that may be a problem.
I'm calling Apple again tomorrow. This expensive, new computer is essentially useless because I repeatedly lose the state of my applications when forced to restart. I'm mad about this. It sounds like a widespread problem, and there's no clear information about causes. I do see this in the system log:
4/9/11 7:57:01 PM configd[15] Wake: Drivers Failure - AC - EHC2
com.apple.message.domain: com.apple.powermanagement.wake
com.apple.message.signature: Drivers Failure
com.apple.message.result: Failure
Is the software failing? Or is the driver failing because the hardware is unresponsive?