Here are some currently-known inadequacies:

urgent
 * Conflicts << installation ordering
 * Version numbers in pre-depends stuff
 * Search for all pre-depends things at once, bomb out if any not found
 * check description in dpkg-deb
 * field overflow in dpkg --list
 * _always_ show section in --yet-to-unpack
 * automatically do --yet-to-unpack in installation methods
 * check depending packages when installing new version.
 * error handling from some dselect actions. 1399
 * Several things ought to be configurable but aren't.
 * Filenames containing newlines.  Conffile names containing spaces.
 * dpkg --status for virtual packages
 * update-alternatives prompting.
 * logging, both transcript logs (kept briefly)
   and action logs (kept forever?)  957
 * start-stop-daemon process status check. 1480
 * remove old docs from /usr/doc/dpkg.
 * WTA: fix translations for dpkg --help which broke after adding --stop-after

other stuff unlikely to get done soon
 * Automatically remove <file>.gz if <file> can't be found ?
 * Local version number (using non-numeric epoch, perhaps ?)
 * Filename field generated by --record-avail handle split packages somehow.
 * understand Replaces in dselect
 * provide way for package to declare ownership of files for dpkg -S
   and -L without having dpkg act on this
 * md5sum component in new .deb files
 * diversions list as control archive entry
 * single maintainer script, and new package getting there first
 * dpkg -s show something for virtual packages
 * settable defaults for update-rc.d
 * local conffiles
 * hooks
 * gzip -0 option for dpkg-deb
 * There is no documentation. 1526
 * newbie interface to dselect. 1037
 * FTP installation method
 * `template' file giving default selections of dselect.
 * start-stop-daemon in C. 1670
 * dselect per-half focus and keybindings improvements. 1555
 * floppy map (where are the files)
 * how to change case of package names
 * support for adding files to dpkg's file lists
 * `fake' or `null' packages
 * --purge remove empty directories which used too contain conffiles
 * conffiles handling options, including `replace removed files'
 * `diff' option at conffile prompt
 * dpkg --query | -Q

done
 * highlight or pre-sort or something new or changed packages,
   during upgrade selection.
 * side-by-side version display
 * version number comparison option
 * Pre-Depends installation ordering
 * a.out version
 * uncomment ELF preinst modification
 * Replaces (auto-deselect for conflicts)
 * Replaces (don't overwrite otherwise)
 * compile with ELF GCC out of the box
 * dpkg --print-architecture
 * Architecture field check
 * symlink rename change
 * dpkg --listfiles should do better for multi-package files  (pkg, pkg: ...)

obsoleted so not done
 * version numbers not starting digit early.
 * dselect bottom window too large, and/or resize