Note for GNOME Later than 3.6
1. libibus maybe compiled as a dependency of gnome, don't try to remove it.
2. Remove package provide /usr/bin/ibus-daemon, to avoid possible conflicts, the package name may vary from distribution to distribution.
3. Since fcitx can already take care of Xkb, you may want to run:
gsettings set org.gnome.settings-daemon.plugins.keyboard active false
4. If you are using fedora, make sure to use imsettings to select "Fcitx".