In my setup with EP45-DS4P, with SnowLeopard, Power Button and WOL Wakes also brings up the display within a second or two. But the 'Wake Reason=' in the log is empty.
However, with Lion the display fails to come up and it just sleeps again within a few seconds. Nevertheless, a tap within the few seconds, on my trackpad or keyboard/mouse brings the display to life. Later checking the unsuccessful wakes in the log show the 'Wake Reason = ?'
On the other hand, my wife's setup on a 945GCM-S2L with GMA 950 graphics, has no such problems in Snow Leopard or Lion. As a matter of fact the kernel log even show the Wake Reason as 'power-button (User)'.
Otherwise, all forms of Sleep (including power-button sleep) and Wake (USB & Bluetooth) works normally.
Over the last couple of weeks, testing out various mods by comparing the two dsdt's proved unsuccessful.
Those of you with GMA950 graphics can confirm if Lion wakes up by the Power Button successfully.
Edited OP on 23 July, 2011 - Include WOL.
Power-button wakes work succesfully on GA-945GCM-S2L with GT220 graphics too.
Overcomes topic's problem with darkwake=0 kernel parameter.