I think `Ember.typeOf` will only return `instance`  for `Ember.Object`

https://github.com/southpolesteve/ember.js/blob/8c71bfa2478625958f0e3bc49a7ba6684ca9aae8/packages/ember-metal/lib/utils.js#L600

Would it be better to get rid of the `Ember.typeOf(model) === "instance"` check completely and only check that `getProperties` is defined?

In any case, do you think it is better to check if  `getProperties` is a function?

```
Ember.typeOf(model.getProperties) === 'function'
```

Or just that it exists?

```
Ember.typeOf(model.getProperties) !== 'undefined'
```