Did you check out Tastypie (http://toastdriven.github.com/django-tastypie/)? It is also RESTful, and explores some similar ideas as a replacement for Piston, but approaches it in a manner similar to Django models.
It’s quite a nice solution actually, but I’m afraid it’s far too coupled with the Django models for many of my use cases. A lot of the time you’ll create a Resource without any model to back it—for example, most Rails projects use a UserSession resource for logging in/out, with logging in => new/create, and logging out => edit/destroy.