I've been using this board since Leopard and currently have it running 10.8.2 with a DSDT. While I'm sure it runs great without a DSDT here's what I did to get this board up and running:
1. Install with UniBeast
2. Download MultiBeast, KextBeast, DSDT.aml (attached below), and toleda's ML Optimized Realtek AppleHDA (ALC 889 kext) from:
http://www.tonymacx86.com/audio/67763-ml-optimized-realtek-applehda-preview-alpha.html
3. Put DSDT.aml and toleda's ALC889HDA kext on the Desktop.
4. Run MultiBeast, with User DSDT option and Drivers > Network > hnak's AppleIntelE1000 driver ONLY
5. Run KextBeast to install ALC889 Audio kext
6. Restart and check to see that audio and Ethernet works. The rear speaker port should be identified as Internal Speakers in the Sound Preference Panel.
*The Mac 3,1 smbios installed by MultiBeast by default should alleviate any memory slot errors
*After updating through System Update, you'll need to reinstall the Audio kext, so keep it handy
*In my case, sleep, shutdown, restart all work great, except that the system will not sleep on its own (not sure why)
*About the DSDT:
---Based on BIOS Rev. 5599
---Standard desktop patches applied + AHCI Orange Icon fix
---HDEF audio patches w/ Audio ID 1