What's all the excitement about XMLHttpRequest

The buzz on many blogs is Google's use of XMLHttpRequest to allow the browser to do requests of the backend without a page refresh. To the best of my knowledge XMLHttpRequest or similar functionality has been part of javascript support in IE and Mozilla for a couple of years. We have been using it for an application at work for the last 20 months to make XMLRPC calls to dynamically update the browser and a SVG view. The biggest issue in the past is getting it to work across browsers, and rather than writing javascript with lots of "if (browser == 'X')" code I would recommend taking at look at the joslait javascript library. As well as providing a set of routines which allow XMLHttpRequest functionality on many browser versions and a XMLRPC client, it has a number of other useful routines.