isComposing

application.controller.js

import Ember from 'ember';

export default Ember.Controller.extend({
  value: '',
  
  updateWithIsComposing(e) {
    if (e.isComposing) { return; }
    this.set('value', e.target.value);
  },
  
  updateWithout(e) {
    this.set('value', e.target.value);
  }
});

application.template.hbs

with <code>isComposing</code>:
<input value={{value}} oninput={{action updateWithIsComposing}}>
<br>
without:
<input value={{value}} oninput={{action updateWithout}}>
<br>
{{value}}

twiddle.json

{
  "version": "0.6.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.3.1/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.3.3/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.2.0/ember-template-compiler.js"
  }
}