I lost faith in AppEngine, partly because of a pratt in England that annoyed the shit out of me, and partly because I couldn't see how to implement the applications I wanted using it. The DataStore, simply, wasn't enough.
It inspired me. Instead of trying to use AppEngine's DataStore as a transactional store, which is something it sucks at, I can instead using it as a pub/sub notification hub.
This would move the query side out to the clients, with their local Gears datastores, and make updates the only part that had to be propagated from the client back up to GAE, and thence out to all the other clients.
It actually works. A complete application deployment platform built from Google's software. Kinda scared right now.