I just followed guide available here (unibeast for ML) as I have briefly described above. After installation I've run MultiBeast and installed woodooHDA (latest version) and IOAHCIBlockStorageInjector (to avoid showing internal disks as external - in orange color) and that was it !!!
The functionality is just the same as in Lion (10.7.4.) - sleep, on-board audio, etc... The only issue I have (both in Lion and ML) is that sound is not working after restart and I have to replug the audio cable. Although it is fully functional after waking up from sleep (not a big deal since I am using sleep all the time).
Again, if you have additional sound card supported by OS X than you should stick with DSDT solution which is much more vanilla.
Nevertheless, I don't know if it is relevant but I have updated my bios back in 2008 using custom bios compiled by BuildSmart (was running 10.5.8. that time).
Hope this will help. Good luck !