In a new post from our sister site, AjaxDeveloper.org, there's information about a new post on Joshua Eichorn's weblog today:

If you use JPSpan to augment a normal website you may have noticed that your page loads now take quite a bit longer. The reason for this is loading the JPSpan client javascript code, its generated on each load and so it can’t be cached on the client. This file can become huge if you register lots of classes with lots of methods to create stubs for.

In the form of a solution, Josh suggests that you cache the page (he uses HTTP_Cache) and caches both the page and the output generated from PHP. He shows you an example, complete with code and instructions on getting it set up for your JPSpan pages...