About a year ago, I switched from AWS to Google App Engine (GAE). To be frank, GAE is a beta quality service, in stark contrast with the mature and elegantly designed Amazon offering. On the other hand, GAE is a higher level service with a killer benefit: it renders system administration obsolete! The are no servers to administrate, no network connections to monitor, no extra services (mail, image processing, backup, etc) to setup and you certainly don't need a DBA to scale the Datastore. Horizontal scaling is automatically catered for and deployment is a no-brainer.

Still, this service needs a lot of improvement. Here are some features I would like to see, sooner rather than later:

Firewall API
The API should allow for easy blocking of dos attacks and restricting access to annoying users and wild robots.

Full Text Search
Come on, this is Google!

Map Reduce
Again, this is Google. Map Reduce is totally required in NoSQL environments (like Datastore).

Asynchronous Datastore calls
Async URLFetch is a great first step, but async Datastore calls would dramatically improve the performance of typical applications.

Support for Servlet 3.0 async model
End to end support for async would allow for implementation of NodeJS-style frameworks on top of GAE.

Blobstore API improvements
This API seems half-baked at the moment. I would like to see a more intuitive, S3-like interface. Better integration with the Image API and support for ETags would be desirable.

Release the source code of the Java SDK
Google already releases the source code of the Python SDK. Releasing the source code of the Java SDK would be extremely helpful for developers of alternative language SDKs (like AppEngineJS).

Multitenancy
Support for multitenancy in the Datastore would trigger an explosion of Web applications on the platform. Moreover, an improved Google Apps Marketplace would be a catalyst in the creation of a viable ecosystem.

Google Programming Cloud Web Technology