Recently I started development on a brand new web site project, which gave me the opportunity to use JQuery with AJAX on the client side.
Luckily for me I chose correctly and JQuery has turned out to be an amazing library with the ability to manipulate the client side DOM with ease and has some nice UI effects like fade, shrink and grow for HTML elements.
My choice has further been backed up by the recent announcement the Microsoft will be distributing JQuery with all their future releases, in addition they will be adding increased intelliscence to the library making it even easier to use. Also all future AJAX Toolkit releases will build on the JQuery library.
To read the full announcement from Scott Guthrie go here