You don't need to login as root to unbind from AD. If you login to single user mode and mount the boot volume read/write, you can remove/backup all the conifg files in /Library/Preferences/DirectoryService. Now reboot and your computer will have lost it's AD bind, though the computer account will still exist on the Domain Controller.

If you already have a local account, you can now login with that, then use fast user switching to login to your old AD account (I had AD account cacheing turned on, so this may not work otherwise).

I'm still working on figuring out what the exact problem and solution is, because AD worked great in the developer seeds....

Cool. I'll go that route, and try to bind it again.

I can't re-bind it, but I was able to clear the binding using that tip.