IPod touch stuck in recovery mode after iOS 6 update error 6

Question

I wanted to sync my iPod touch with my Mac last night, when iTunes tried to sell me on the iOS 6 update.  I told it to go ahead with the update, and left it alone to do its thing.  When I checked again, it told me the update had failed with error 6, and that I might need to restore my iPod.  The only info I've found about error 6 pertains to Windows security software, and that clearly does not apply to my case.
The iPod is now stuck in recovery mode, and none of the my googling has changed that.  I have tried the various patterns of power and home keys, and have also tried downloads that were supposed to force the iPod out of recovery mode.  How exactly does an update brick a device?  Now I don't mind restoring the iPod, but I need to get my data back.  Loosing the data is not acceptable.  This is not a jailbreak attempt.  I just want my data back, and I don't mind going low-level to get it (i.e. terminal, dd, scripts, ...).  Pointers in the right direction would be greatly appreciated.

Answer 1

I was able to extract my data and copy it to a disk image with the help of http://code.google.com/p/iphone-dataprotection/wiki/README.  This process is really only appropriate for developers, I regret to say, but for developers the process is reasonably robust.  I still had to read between the lines in one or two places, and make good use of the shell, but I am delighted to have retrieved my data from my iPod.
A lower priority question for me is whether to try to collect my notes and contacts from the assorted .sqlitedb files.  It looks like iFunBox may come in handy if I try to push things back onto the iPod once I restore it.
For anyone who cares to know, my iPod Touch decided to listen on port 2000 instead of port 2222, my /dev/rdisk0sXsY devices had different numbers than expected by dump_data_partition.sh, and I had to find my keychain-2.db file in /mnt2/Keychains on the data filesystem.  But it worked, and that's awesome.