I've tried a few ways to restore the Mountain Lion InstallESD.dmg to a USB hard drive to reinstall on my Mac Mini. I've used Disk Utility Restore, Lion Disk Maker and Carbon Copy Cloner.
Each method gives me the same outcome: When booting I get the infamous circle with the slash and spinning gear.
I've tried to boot up with the same USB on multiple macs and they both have the same outcome. And yes, the Macs I'm trying it on have the compatibility to support Mountain Lion.