Yes, I've used localStorage. It's supported well across all the main browsers, it's reasonably quick, and it'll store more than enough data for your app. It's really just a case of doing (assuming you include JSON2.js);

  var ls = window.localStorage;
  var config = JSON.parse(ls.getItem('config')); //load the config

  ls.setItem('config', JSON.stringify(config)); //save the config

That's pretty much it. You'll need to protect against the config not being there, but that's just a matter of using a default empty object if config is null.