Note for GNOME Later than 3.6
1. libibus maybe compiled as a dependency of gnome, don't try to remove it (If you're not using gentoo).
2. Remove package provide /usr/bin/ibus-daemon, to avoid possible conflicts more easily, the package name may vary from distribution to distribution.
Disclaimer: We don't try to be evil here, like 360 vs QQ, but as for the reason you to uninstall IBus, you should check here, this fix merged into 3.6.1. GNOME 3.6 make other input method framework not usable, if it detect IBus is installed and IBus integration enabled at compiling time.
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".
Fedora doesn't use imsettings to start input method under gnome3 anymore (but still it will set the environment variable). So remember to use gnome-session-properties to add an auto start entry.