Hi
Sharing any success at all, literally.
I am using a Megabyte GA-Z68X-UD3H-B3 Rev 1.0 board, with Sapphire ATI 5770. Have managed using Unibeast to get install screen & install (fairly straight forward ), could not get past white display after booting to USB again, then selecting the drive onto which I had installed ML. Finally got to ML login screen (by typing -x -v) (as if I had shut down and needed to log in) which just looped back to itself on completing correct password for the computer. Could not get past this stage so wiped an SSD and tried clean install to that which got me to ML select your country and get Internet working, which I am unable to get past. The SSD I selected is too small to migrate all of my installed software to so am am going to install onto my bigger SSD - am considering using the Move method rather than Unibeast.
I think that the 5770 is quite compatible, a lot of trouble has stemmed from my trying to install using upgrade (which means a lot of my previous multi beast tweaks remain to interfere with new ML - therefore have decided that clean install is the only way to go! Lion looks to have a nice migration via the install progress to enable installed software to be bought onto the new Operating system, which is what I wanted to avoid, just did not want to install all of that stuff!!
Cheers