Google updated the App Engine SDK to version 1.1.5 today (release notes).
Among the new features, the one that really caught my eye was: "Sped up the datastore stub."
I didn't notice a speed up in the initial start-up time of the dev server with a large datastore, but it does seem that my app is more responsive. I need to test further and get some real data though.
One thing I've noticed is that the mean time between SDK releases has been decreasing quite considerably as of late. I hope that means that development on App Engine is speeding up and that we'll start seeing new feature implementations on the deployment environment also.
The SDK 1.1.5 released – App Engine development speeding up? article by Aral Balkan, unless otherwise expressly stated, is licensed under a Creative Commons Attribution-Noncommercial 2.0 UK: England License.
We had finally gotten sick of the load times for the static files on the dev appserver, so two days ago we hacked together a mechanism to load static files from a Python SimpleHTTPServer that runs concurrently with the dev appserver, when running locally. Instead of taking 2/3 of a second to load each static file, they all load instantly. I have no idea why each request was being served so slowly; it was much slower than the datastore bits, for our app.