Thanks for your work. I have a 8530w and install the Mountain lion DP2 successfully by use your dsdt. Cpu is T9600, seems speedstep works. DVD also works. I download a DSDT from an Chinese forum, the author says that it fixed the Brightness control by add Device (PNLF), also get DSDT + AppleHDA.kext working (10.6.7) and sleep works fine. But this DSDT result black screen to me.
I fixed this dsdt and it doesn't result in black screen now. You guys can try it. Use scroll and pause to control the brightness, and use the attached applehda.kext. Sound works fine, auto-switch between speaker and headset. But the microphone still not work. Sleep also works fine. Use Fn+F3.
Here is the DSDT and modified AppleHDA.kext.