1) .desktop file should not use absolute path.
2a) debian/rules should contain the following additional rule:
binary/gconf-cleaner::
dh_desktop -p gconf-cleaner
2b) Consider also using /usr/share/cdbs/1/class/gnome.mk
(Choose your favorite: 2a or 2b)
3) You might want GCONF\(hyCLEANER instead of GCONF-CLEANER in the manpage
4) Your debian/copyright should license the packaging, as:
The Debian packaging is (C) 2007, Jeremy Teale <orion@hypnogogic.org>
and is licensed under the GPL, see above.