The Embedded App SDK is already successfully powering many Shopify-created apps. These provide a great example of what is possible with the EASDK. Although they appear to be native Shopify features, these are in fact separately hosted and use the Shopify API and the Embedded App SDK to great effect.
Example Ruby on Rails app
Shopify provides a simple app built with Ruby on Rails to provide an example implementation of every API call available in the Embedded App SDK.