VERY IMPORTANT NEWS EVERYONE
YOU DO NOT NEED TO REFLASH

I just hit CTRL+C a couple times and it will kill that script (the one which prints "Installing updates do not interrupt" to the console) and allow the phone to continue booting!! (I also hit 'u' a couple times because thats the bootloader key but I doubt that did anything.)

You don't need a new battery or a flasher or anything, just Ctrl-C.

Once you've rebooted you will need to repair the packaging system state with dpkg from the command line (I haven't done that yet but it should be easy, I've done it several times on a full debian box, and once on the phone.)