This is what I did.
Downloaded the GM
Backed up to icloud.
Used itunes11.05 to restore ipad with the GM. Once the GM is installed, you will get an error message stating you can not connect this device to iTunes unless you have iTunes 11.1
I then unplugged from iTunes and continued the restore using the icloud backup.
But, you will not be able to connect your device to iTunes again until 11.1 for windows is released.