Because app-engine-patch includes more than just a zipped package of Django 1.1. It comes with jQuery, the Blueprint CSS framework, a media generator to join and minify your CSS and JavaScript, automatic URLs for each app (using urlsauto.py), and helper functions like ragendja.template.render_to_response and ragendja.dbutils.get_object_or_404.
Got it. I just wondered if there were standard-Django features you wanted to use, but couldn't (easily) without AEP. It sounds, however, like it was all the other in-package goodies that made AEP desirable.
If there were a "GAE django starter project" that included jQuery etc. but made use of use_library(), would that be interesting?
Yes, that would be interesting because the startup time for loading the zipped Django 1.1 package is significant. Maybe app-engine-patch can be tweaked to use_library()?