I haven't messed with AJAX yet, and I don't have any immediate plans to do so. For those not familiar, AJAX stands for Asynchronous JavaScript and XML, although it's most famous use is in the cool interface for Gmail (I still have invites if you want them!).

Anyway, over on the Apress blog, Harshad Oak has a post asking if it's even worth adopting. His points really hit home after dealing with a fair amount of Javascript on my last project. Basically, he asks how can we expect to get cross-browser support for AJAX if we're already struggling to get cross-browser support for basic HTML, Javascript, and CSS now? He makes a very good point. I can see using AJAX on an intranet where you can control the browsers used, but out in the vast internet space, I'm not so sure. I guess you have to do what Google does - provide an alternate version.

Having said that, if you want to work with AJAX and ASP.NET, you'll want to read this blog. He wrote AJAX.NET, a wrapper for working with asynchronous callbacks and .NET.

UPDATE: Here's another AJAX implementation for ASP.NET.