We have purchased several Dell Optiplex 780's with the Intel 82567LM Based Network controller. All of our other Dells have been able to Wake on Lan from either our Altiris console, or Vision clients (in our computer labs). However, the 780's will not respond to a WOL.
I have disabled the low power mode, and set it to remote wake up enabled.
These have the Intel Management Engine on them, but I'm not sure if anything in there affects the WOL.