I dont think I can help much since I have never heard of this function before but after a read into it. I got a good article here:
http://en.wikipedia.org/wiki/AJAX

One of the pros and cons it tels is that on somethings you cant press the back button because the data is made dynamically without reloading the page and search engines wont be able to pick up the dynamic data. Offcourese people need to have javascript running.
But still looks like it can be some time and bandwidth saver for the client.
I hope someone can give you more useful info than I did.