I logged in to my google reader account today and found an interesting link called "Offline" on the upper right hand corner of the page.
Clicking it launches a window that prompts me to install Google Gears that will apparently enable google reader to work offline.
Upon visiting the developer guide for Google Gears, it seems there are some components it has that may be beneficial towards speeding up an ajax web app, like, for instance, the workerpool.
I am going to install it and give it a go. Most people are on broadband anyway so I don't quite see why an Offline app would be any use, unless of course you're constantly on the go, leeching free wi-fi internet access anywhere you can get it.