Well, here it comes...

debian

• Reads configuration from ~/.chroot; all defaults are the same.
• Since hilda is now obsolete (see below) it now drops a file in /debian/tmp/ to mark chroot ready; this is actually more robust, as cancelling after the filesystem is mounted won't leave it persuaded everything's cool.
• The mount point may be changed from the default of /debian

debbie:

• debbie with no arguments now drops you to a non-privileged chrooted shell.
• hilda is now obsolete; debbie now passes su through to debian, as needed for above; eliminating one Debian-side script is a nice side-benefit.)
• DISPLAY is preserved, if it exists. (I think it should always be set, normally to :0.0, but not sure.) Good for multi-Xomap, USB-VGA, or otherwise multi-X-server configs, with no change for standard config.
• User to drop to is now configurable; defaults to user, of course, but can be set...
• Reads the same ~/.chroot as debian

.chroot

• Example config with defaults documented in comments.

Overall comments: Changed a lot of things that were set as environment variables (export FOO=bar) are now shell variables (FOO=bar); indentation is changed to "correct" style, efforts to safely quote things to prevent complete breakage in the event of empty or space-containing definitions...

EDIT: Updated tar. All better now, sorry about that.