I'm not sure if you're worried about this, but this is not really the "Backbone" way.  This is prime area for a model and view to handle this; and eventually it could probably handle the $.ajax call above in the `func:` function.

I'm sure it's fine for the debug page, but I'd like to see a proper model/view something like

```javascript
var UpdateModel = Backbone.Model.extend({
    defaults: {
        isUpdateAvailable: null
    },

    url: Ghost.settings.apiRoot + '/update/'
});

var UpdateView = Backbone.View.extend({
    initialize: function () {
        this.listenTo(this.model, 'change:isUpdateAvailable', this.handleUpdateResponse, this);
        this.listenTo(this.model, 'error', this.handleUpdateCheckError, this);
    },

    handleUpdateResponse: function () {
        if (!this.model.get('isUpdateAvailable')) {
            Ghost.notifications.addItem({
                type: 'success',
                message: 'Ghost is up to date.',
                status: 'passive'
            });    
        }

        self.confirmUpdate(this.model.toJSON());
    },

    handleUpdateCheckError: function (xhr) {
        Ghost.notifications.addItem({
            type: 'error',
            message: 'There was a server problem',
            status: 'passive'
        });
    }
});

// Then use it something like this
var updateView = new UpdateView({
    model: new UpdateModel()
});

updateView.model.fetch();
```

You could also work it out to use a `model.save()` in place of the code above using an $.ajax call by adding some more attributes.

Just a thought.  I really like Backbone.  What you have is straight forward and gets the job done though, it just won't scale well to have $.get and $.ajax everywhere.