I got a refurb 2012 iMac with a 1TB Fusion drive to replace a 2010 Mac Pro with 1TB 7200 HDD, both I bought for the use of video editing and motion graphics programs. Sadly, migration failed twice when I tried it via Ethernet, stalling at "34 minutes remaining" both times after about 4 hours.
This gave me the error "Restore failed - resource busy" error. I tried again two more times making sure I was using the indented drive partition from the Disk Utility list, "Restore Failed" every time.
So now I had a completely wiped hard drive in my iMac, no OS, nothing. With my external still plugged in, I restarted holding option and booted to the recovery disk where I tried simply to re-install Mountain Lion on the iMac drive. This is where it get's weird.
I get to the "Preparing to install" screen and it says 9 hours, which seems incredibly long for an OS download, but I figure it'll drop quickly so I step out for a bit. When I come back, the computer is back to the first boot screen from which I choose which action I want to do: Install OSX, Restore from Time Machine, etc. Basically it's back to the start without any errors or buttons to be clicked or anything.