Hey very nice. Seems like similar experiences as we've been doing our server-calls RESTful style too, and came up with tricks for sencha performance (gzipping/concatenation/minification, lazy rendering, buffered loading), and still supporting several openacs-based apps with newer interfaces.
One interesting thing I did reduced large amounts of reliance on tcl for an 'excel-like' interface that required all of the logic in the browser (for offline support). It was for what-if scenarios in the human resources work was write my own library for the client and re-use it on the backend in a plv8 function (javascript inside postgres). Openacs did nothing except handle the request and call the database function (after error checking, permissions). It allowed us just to 'replay' the front end actions in the database to keep the server in sync.
It would be interesting to have a chat one day and share techniques, especially relating to sencha, and patterns for highly dynamic apps. We could share a few things we've done that might have crossover to your apps, and vise versa (your ticket tracking app sounds cool).
Taras
