Zotac IONITX - Wake on USB
I have the newer board revision (with the J3 jumper) that supports Wake on USB. Somehow that translated to "Wake immediately!" for me, and many others judging by the googling I've done. The system goes to sleep, then immediately wakes up. Very annoying. Also very easily fixed if you don't care about USB speed.... Disabling USB 2.0 support fixes the problem. Don't know what (can't even really imagine), but changing that one BIOS setting allows it to sleep peacefully.
As for waking up, assuming /proc/acpi/wakeup has the correct option enabled (mine was by default), it should work if J3 is in the default position. If you have an MCE/compatible iR receiver, and it doesn't seem to be working, make sure you use an MCE remote, and push the power button. I had stuffed the original MCE remote in a drawer in favor of a much nicer (IMHO) remote, and couldn't figure out why my machine wouldn't wake up. I stumbled across the an article that had the answer... I guess it makes sense that a stray iR signal shouldn't trigger a wake-up, but now I have to come up with a different remote. Oh well, at least it works.
So there you have it... this board (or I suppose the MCE rx could be at fault) needs USB 2.0 disabled for ACPI sleep to work. Go figure.