Anyone out there using AppEngine for anything interesting nowadays?

I was originally excited about it, but the performance and limits have kept me from feeling comfortable hosting something substantial there. This feels like maybe an odd bias that stems from it not being as awesome as I wanted it to be, so it'd be great to hear some successful anecdotes from others here.

I'm now running a homepage (http://www.billkatz.com) on my open-source blog software for App Engine (Bloog). I've included a python shell accessible via your web browser. It's like a limited rails console that lets you mess with your app and datastore in the cloud. (No ssh into App Engine.) Also recently added sharded counters as per some best practices suggested by Google.

I'll report on a more substantial app once it gets some testing.

A good list of apps on App Engine: http://appgallery.appspot.com/

I'm working on a web app clone of Axis & Allies. It's using Google Maps (with the game board overlaid) as the UI.

Much needed DataStore update. App Engine is slowly but surely becoming an option for serious production apps.