My project runs on CouchApp/CouchDB, with JQM for the UI. I use _lists and _shows to render html, which JQM then loads asynchronously. These XHR calls are cached and even though I've updated a document (and deleted the DOM cache), subsequent XHR calls to the same resource URL return 304 (maybe due to Etags on the _list and _show responses). To work around this, I've added "cache: false" to the $.ajax call in loadPage. I've tried ifModified as well, but it doesn't do anything it seems.
I propose that there be an API that will allow us to mixin our own custom options to the $.ajax call, or at least allow us to play with the "cache" and "ifmodified" values.