I've being checking your site if you added new tutorial. This Ajax requests one looks very good except the sound quality (my office was really noisy

).
Actually, I really don't know much about JavaScript and Ajax.
After this tutorial, I got this tutorial will not work on IE6/7 and Firefox 3.0 or above unless if we include JavaScrip JSON parser script. If you have time please consider how we can include and use jQuery JSON parser. And you didn't mention how it would be on Google Chrome.
Actually, it is a little bit difficult to see the javascript code. Is there any simple and Zend-like way to use Ajax without duplicating many things you mentioned?