Do you have a Time Machine backup of your last Snow Leopard installation? I had the GM on my Mac and just booted from the restore DVD that came with my mac and did a regular "restore from backup" with Time Machine. No problems.
EDIT: this is a one-way trip. I have another disk with my last GM Lion install. I could not "restore from backup" back up to OS X Lion while booted into a Snow Leopard disk.