nautilus does not draw previews for files (especially for ones that it could preview before)
	nautilus gets confused about files it should recognize (e.g. it sees .jpg's as "jpg document", a custom type, rather than the proper "JPEG Image" type built into gnome)
	.desktop files lose their magic (launchers look like plain text)
	icons are missing and do not show from gnome's menus, and the themes control panel complains bitterly
	there are missing menu items

half of gnome is using /opt/gnome/share and the other half is using /usr/share

move the affected directories' contents into either one or the other and symlink the other one. (the important ones are icons, pixmaps, mime, mime-info)

Also clear out your ~/.local/ dir, as bad mime data is cached there. might also want to clear ~/.thumbnails/fail.