AppEngine Datastore limitations

I've been trying to decide if moving urlBorg to Google App Engine is a good idea. The pros are obvious: scalability. There are many features I've wanted to implement for urlBorg but never did because I'm afraid that if it turns into a hit, my server will go down.

I mean, creating short URLs is a trivial thing. If you want to make a service that stands out, it has to be that it takes care of the little details in a much better way than the rest. And you have to be sure that your service will be able to scale.

So, moving urlBorg to Google App Engine should be a no brainer, right? Wrong.

My main issue is AppEngine Datastore.

The App Engine datastore is not a relational database. While the datastore interface has many of the same features of traditional databases, the datastore's unique characteristics imply a different way of designing and managing data to take advantage of the ability to scale automatically.

So, forget about queries involving group functions like count(*), min(), max()... :-(

I wish they had some good examples on how to use the AppEngine Datastore to do data mining. How should/would a "web analytics" application be implemented using AppEngine for example?