I have a fully functioning xw8600 on 10.7.4.
-Dual x5450
-4gb ram
-Quadro FX1700
-Sound works with latest VoodooHDA
-2x SATA HD's connected to SAS controller (SATA ports function as well) Had to add device ID to the LSIFusion Kext, don't recall actual kext name. Really was just trying to get SAS controller working, then never switched back to SATA out of laziness!
-Working ethernet with BCM5722D.kext, had to edit info.plist and add my device ID.
-Sleep/wake from sleep works, have to use PleaseSleep to initiate sleep, wakes with single mouse/keyboard click.
Bios is set to RAID+AHCI, also worked on Combined IDE (I think, it was whichever IDE mode which supportes 4 SATA ports)- can post exact bios config when I am at the computer.
Install wasn't done using methods which I can discuss on this board (TonyMac methods), feel free to PM me and I can provide details when I get home from the office.
In short, installed using aforementioned method, only installed latest FakeSMC and NVClock plugin (no other plugins work as it has an SMSC SuperIO controller) I get monitoring of HD's, CPU tempa (only one of them, I think), GPU fans/temps, but no system/CPU fans or other temps. Graphics work with GraphicaEnabler=yes, no sleep enabler/NullCPUPWM kexts, IntelCPUPwm loads fine and I achieve either a 6x or 9x multiplier.