IME under Windows
There is an issue which causes the IME window to appear in a wrong position.
The correct position should be at the cursor just like typing English.
By the way, this plugin (IMESupport) fixes the issue.
ibus and fcitx under Linux (or at least Ubuntu)
There is another input method issue for ibus and fcitx under Linux which makes them totally unusable.
And someone gives it a solution here.