atoms, the audio problem seems to be related to the DSDT.aml needing to be slightly different beteen minis. In my case 7.5 fixed it, but I believe a previous post indicated that 7.1 -> 7.5 caused him to have a problem. You could back up DSDT.aml prior to running the script and restore if you have to.
I had no problems with video with either version. Not sure about sleep or SD card as I still have the 16GB STEC drive and heard it would not sleep. Have you got sleep working on yours?
I did the 10.5.6 update prior to the 7.5 script and had zero problems with either step, although some people obviously have.
Don't know if this will help you, but good luck. Time Machine backup does work if you want to go that route