A basic example of how to benchmark react component render times.

react-benchmark.js

'use strict';

import _ from 'lodash';
import React from 'react';
import AppActions from '../../actions/AppActions';
import NewsStore from '../../stores/NewsStore';
import { NewsList } from '../';

let { Perf } = React.addons;

function getState(state) {
  return _.merge({
    posts: NewsStore.getAll(),
    isLoading: true
  }, state);
}

class NewsPage extends React.Component {

  constructor(...args) {
    super(...args);
    this.state = getState();
    this.onChange = this.onChange.bind(this);
  }

  componentDidMount() {
    NewsStore.addChangeListener(this.onChange);
    AppActions.getNews();
  }

  componentWillUnmount() {
    NewsStore.removeChangeListener(this.onChange);
  }

  onChange() {
    Perf.start();
    this.setState(getState({
      isLoading: false
    }));
    Perf.stop();
    Perf.printInclusive();
    Perf.printWasted();
  }

  getNewsList() {
    return (
      <NewsList
        hasError={this.state.hasError}
        isLoading={this.state.isLoading}
        posts={this.state.posts} />
    );
  }

  render() {
    return (
      <div className={'mui-app-content-canvas'}>
        {this.getNewsList()}
      </div>
    );
  }
}

export default NewsPage;

I'm not sure this would be testing the render time as setState is batched in event handlers meaning not only has the DOM not been updated the components render method hasn't even been called by the time you call Perf.stop.

I think it would be better to call Perf.start in componentWillMount / componentWillUpdate and call Perf.stop in componentDidMount / componentDidUpdate as then you can be sure the render operations have been flushed to the DOM.