One upcoming feature of Google App Engine that's worth mentioning is large-scale data import and export. We know that many of you have large apps that already run on other platforms, and getting all of that data into the Datastore API is a challenge. And, conversely, we also know that a lot of you want to make sure it's easy to move off Google App Engine in the future, in case you need to switch to a different platform.
With Google App Engine, you own all the data in your app. As stated in our terms, you always have the right to get your data out of Google App Engine at any point. We wouldn't have it any other way.
To that end, we would like to solicit feedback on what form you would like the data exporter feature to take. We've started a thread in the discussion group about this, and we'd love to hear what you think. XML output? CSV transform? AtomPub? RDF? Let us know!