Google App Engine (GAE) is focused on making development easy, but limits your options. Amazon Web Services is focused on making development flexible, but complicates the development process. Real enterprise applications require both of these paradigms to achieve success… What we really want is the flexibility of AWS and the simplicity of GAE.
For the rest of the post see http://natishalom.typepad.com/nati_shaloms_blog/2009/06/google-app-engine-plus-amazon-aws-best-of-both-worlds.html