I use an EFI String combined with the AppleIntelX3100FB.kext vers. 1.5.18 and i have proper brightness control.

Links:

http://www.insanelymac.com/forum/ind...howtopic=87574

see attached files: X61_BrightnessPack.zip

By the way, i got Vanilla speedstepping working too, and many other fixes in my dsdt.